{"id":74483,"date":"2026-02-09T21:49:05","date_gmt":"2026-02-09T13:49:05","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/74483.html"},"modified":"2026-02-09T21:49:05","modified_gmt":"2026-02-09T13:49:05","slug":"%e4%b8%80%e7%af%87%e6%96%87%e7%ab%a0%e6%90%9e%e6%b8%85%e6%a5%9a%e6%95%b0%e6%8d%ae%e5%ba%93%e4%b8%8b","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/74483.html","title":{"rendered":"\u4e00\u7bc7\u6587\u7ae0\u641e\u6e05\u695a\u6570\u636e\u5e93(\u4e0b)"},"content":{"rendered":"

\u5355\u8868\u7ea6\u675f_\u4ecb\u7ecd<\/h3>\n

\u7ea6\u675f\u4ecb\u7ecd:
\n\u6982\u8ff0:
\n\u7ea6\u675f\u53ef\u4ee5\u7406\u89e3\u4e3a\u5728\u6570\u636e\u7c7b\u578b\u7684\u57fa\u7840\u4e0a, \u7ee7\u7eed\u90fd\u67d0\u5217\u6570\u636e\u503c \u505a\u9650\u5b9a, \u4f8b\u5982: \u4e0d\u80fd\u91cd\u590d, \u4e0d\u80fd\u4e3a\u7a7a\u7b49\u2026
\n\u4e13\u4e1a\u7248: \u7ea6\u675f\u662f\u7528\u6765\u4fdd\u8bc1\u6570\u636e\u7684\u5b8c\u6574\u6027 \u548c \u5b89\u5168\u6027\u7684.
\n\u5206\u7c7b:
\n\u5355\u8868\u7ea6\u675f:
\n\u4e3b\u952e\u7ea6\u675f: primary key
\n\u7279\u70b9: \u975e\u7a7a, \u552f\u4e00, \u4e00\u822c\u7ed3\u5408 auto_increment(\u81ea\u52a8\u589e\u957f) \u4e00\u8d77\u4f7f\u7528.
\n\u975e\u7a7a\u7ea6\u675f: not null
\n\u7279\u70b9: \u8be5\u5217\u503c\u4e0d\u80fd\u4e3a\u7a7a, \u4f46\u662f\u53ef\u4ee5: \u91cd\u590d.
\n\u552f\u4e00\u7ea6\u675f: unique
\n\u7279\u70b9: \u8be5\u5217\u503c\u4e0d\u80fd\u91cd\u590d, \u4f46\u662f\u53ef\u4ee5: \u4e3a\u7a7a.
\n\u9ed8\u8ba4\u7ea6\u675f: default \u9ed8\u8ba4\u503c
\n\u7279\u70b9: \u5982\u679c\u6dfb\u52a0\u6570\u636e\u7684\u65f6\u5019\u6ca1\u6709\u7ed9\u503c, \u5c31\u7528\u9ed8\u8ba4\u503c\u586b\u5145. \u7c7b\u4f3c\u4e8ePython\u4e2d\u7684 \u7f3a\u7701\u53c2\u6570(\u9ed8\u8ba4\u53c2\u6570)
\n\u591a\u8868\u7ea6\u675f:
\n\u4e3b\u5916\u952e\u7ea6\u675f: foreign key<\/p>\n

# ——————— \u5355\u8868\u7ea6\u675f ———————<\/span>
\n\/*
\n\u7ea6\u675f\u4ecb\u7ecd:
\n \u6982\u8ff0:
\n \u7ea6\u675f\u53ef\u4ee5\u7406\u89e3\u4e3a\u5728\u6570\u636e\u7c7b\u578b\u7684\u57fa\u7840\u4e0a, \u7ee7\u7eed\u90fd\u67d0\u5217\u6570\u636e\u503c \u505a\u9650\u5b9a, \u4f8b\u5982: \u4e0d\u80fd\u91cd\u590d, \u4e0d\u80fd\u4e3a\u7a7a\u7b49…
\n \u4e13\u4e1a\u7248: \u7ea6\u675f\u662f\u7528\u6765\u4fdd\u8bc1\u6570\u636e\u7684\u5b8c\u6574\u6027 \u548c \u5b89\u5168\u6027\u7684.
\n \u5206\u7c7b:
\n \u5355\u8868\u7ea6\u675f:
\n \u4e3b\u952e\u7ea6\u675f: primary key
\n \u7279\u70b9: \u975e\u7a7a, \u552f\u4e00, \u4e00\u822c\u7ed3\u5408 auto_increment(\u81ea\u52a8\u589e\u957f) \u4e00\u8d77\u4f7f\u7528.
\n \u975e\u7a7a\u7ea6\u675f: not null
\n \u7279\u70b9: \u8be5\u5217\u503c\u4e0d\u80fd\u4e3a\u7a7a, \u4f46\u662f\u53ef\u4ee5: \u91cd\u590d.
\n \u552f\u4e00\u7ea6\u675f: unique
\n \u7279\u70b9: \u8be5\u5217\u503c\u4e0d\u80fd\u91cd\u590d, \u4f46\u662f\u53ef\u4ee5: \u4e3a\u7a7a.
\n \u9ed8\u8ba4\u7ea6\u675f: default \u9ed8\u8ba4\u503c
\n \u7279\u70b9: \u5982\u679c\u6dfb\u52a0\u6570\u636e\u7684\u65f6\u5019\u6ca1\u6709\u7ed9\u503c, \u5c31\u7528\u9ed8\u8ba4\u503c\u586b\u5145. \u7c7b\u4f3c\u4e8ePython\u4e2d\u7684 \u7f3a\u7701\u53c2\u6570(\u9ed8\u8ba4\u53c2\u6570)
\n \u591a\u8868\u7ea6\u675f:
\n \u4e3b\u5916\u952e\u7ea6\u675f: foreign key
\n*\/<\/span>
\n— 1. \u521b\u5efa\u6570\u636e\u5e93.<\/span>
\ndrop<\/span> database<\/span> tb;<\/span>
\ncreate<\/span> database<\/span> tb charset<\/span> 'utf8'<\/span>;<\/span>
\n— 2. \u5207\u5e93.<\/span>
\nuse<\/span> tb;<\/span>
\n— 3. \u67e5\u770b\u6570\u636e\u8868.<\/span>
\nshow<\/span> tables<\/span>;<\/span>
\n— 4. \u521b\u5efa\u6570\u636e\u8868, \u7528\u4e8e\u6f14\u793a\u5355\u8868\u7ea6\u675f.<\/span>
\ncreate<\/span> table<\/span> if<\/span> not<\/span> exists<\/span> stu(<\/span>
\n id int<\/span> primary<\/span> key<\/span> auto_increment<\/span>,<\/span> # id\u5217, \u4e3b\u952e\u5217(\u975e\u7a7a,\u552f\u4e00), \u81ea\u589e<\/span>
\n name varchar<\/span>(<\/span>10<\/span>)<\/span> not<\/span> null<\/span>,<\/span> # \u59d3\u540d, \u4e0d\u80fd\u4e3a\u7a7a<\/span>
\n phone varchar<\/span>(<\/span>11<\/span>)<\/span> unique<\/span>,<\/span> # \u624b\u673a\u53f7, \u552f\u4e00<\/span>
\n gender varchar<\/span>(<\/span>2<\/span>)<\/span>,<\/span> # \u6027\u522b, \u6ca1\u6709\u9650\u5b9a.<\/span>
\n address varchar<\/span>(<\/span>10<\/span>)<\/span> default<\/span> '\u5317\u4eac'<\/span> # \u9ed8\u8ba4\u7ea6\u675f<\/span>
\n)<\/span>;<\/span>
\n# 5. \u5f80\u8868\u4e2d\u6dfb\u52a0\u6570\u636e, \u7528\u4e8e\u6d4b\u8bd5: \u7ea6\u675f.<\/span>
\n# \u6b63\u5e38\u6dfb\u52a0\u7ed3\u679c<\/span>
\ninsert<\/span> into<\/span> stu values<\/span>(<\/span>null<\/span>,<\/span> '\u6768\u8fc7'<\/span>,<\/span> '111'<\/span>,<\/span> '\u7537'<\/span>,<\/span> '\u4e0a\u6d77'<\/span>)<\/span>;<\/span>
\ninsert<\/span> into<\/span> stu values<\/span>(<\/span>null<\/span>,<\/span> '\u90ed\u9756'<\/span>,<\/span> '222'<\/span>,<\/span> '\u7537'<\/span>,<\/span> '\u5e7f\u5dde'<\/span>)<\/span>;<\/span>
\ninsert<\/span> into<\/span> stu values<\/span>(<\/span>null<\/span>,<\/span> '\u9ec4\u84c9'<\/span>,<\/span> '333'<\/span>,<\/span> '\u5973'<\/span>,<\/span> '\u6df1\u5733'<\/span>)<\/span>;<\/span>
\n# \u6d4b\u8bd5 \u9ed8\u8ba4\u7ea6\u675f<\/span>
\ninsert<\/span> into<\/span> stu(<\/span>id,<\/span> name,<\/span> phone,<\/span> gender)<\/span> values<\/span>(<\/span>null<\/span>,<\/span> '\u5c39\u5fd7\u5e73'<\/span>,<\/span> '444'<\/span>,<\/span> '\u7537'<\/span>)<\/span>;<\/span>
\n# \u6d4b\u8bd5 \u975e\u7a7a\u7ea6\u675f.<\/span>
\ninsert<\/span> into<\/span> stu values<\/span>(<\/span>null<\/span>,<\/span> null<\/span>,<\/span> '555'<\/span>,<\/span> '\u5973'<\/span>,<\/span> '\u6df1\u5733'<\/span>)<\/span>;<\/span> # \u62a5\u9519, Column 'name' cannot be null<\/span>
\n# \u6d4b\u8bd5 \u552f\u4e00\u7ea6\u675f<\/span>
\ninsert<\/span> into<\/span> stu values<\/span>(<\/span>null<\/span>,<\/span> '\u9ec4\u84c9'<\/span>,<\/span> '555'<\/span>,<\/span> '\u5973'<\/span>,<\/span> '\u6df1\u5733'<\/span>)<\/span>;<\/span>
\ninsert<\/span> into<\/span> stu values<\/span>(<\/span>null<\/span>,<\/span> '\u9ec4\u84c9'<\/span>,<\/span> null<\/span>,<\/span> '\u5973'<\/span>,<\/span> '\u6df1\u5733'<\/span>)<\/span>;<\/span>
\ninsert<\/span> into<\/span> stu values<\/span>(<\/span>null<\/span>,<\/span> '\u9ec4\u84c9'<\/span>,<\/span> '555'<\/span>,<\/span> '\u5973'<\/span>,<\/span> '\u6df1\u5733'<\/span>)<\/span>;<\/span> # \u62a5\u9519, Duplicate entry '555' for key 'phone'<\/span>
\n# 6. \u67e5\u770b\u8868\u6570\u636e.<\/span>
\nselect<\/span> *<\/span> from<\/span> stu;<\/span>
\n# 7. \u67e5\u770b\u8868\u7ed3\u6784<\/span>
\ndesc<\/span> stu;<\/span><\/p>\n

\u5355\u8868\u67e5\u8be2_\u7b80\u5355\u67e5\u8be2<\/h3>\n

\u5355\u8868\u67e5\u8be2, \u5b8c\u6574\u67e5\u8be2\u683c\u5f0f\u5982\u4e0b:
\nselect
\n[distinct] \u5217\u540d1 as \u522b\u540d, \u5217\u540d2 as \u522b\u540d, \u2026
\nfrom
\n\u6570\u636e\u8868\u540d
\nwhere
\n\u7ec4\u524d\u7b5b\u9009
\ngroup by
\n\u5206\u7ec4\u5b57\u6bb5
\nhaving
\n\u7ec4\u540e\u7b5b\u9009
\norder by
\n\u6392\u5e8f\u5b57\u6bb5 [asc | desc]
\nlimit
\n\u8d77\u59cb\u7d22\u5f15, \u6570\u636e\u6761\u6570;<\/p>\n

# ——————— \u5355\u8868\u67e5\u8be2 -> \u7b80\u5355\u67e5\u8be2 ———————<\/span>
\n\/*
\n\u5355\u8868\u67e5\u8be2, \u5b8c\u6574\u67e5\u8be2\u683c\u5f0f\u5982\u4e0b:
\n select
\n [distinct] \u5217\u540d1 as \u522b\u540d, \u5217\u540d2 as \u522b\u540d, …
\n from
\n \u6570\u636e\u8868\u540d
\n where
\n \u7ec4\u524d\u7b5b\u9009
\n group by
\n \u5206\u7ec4\u5b57\u6bb5
\n having
\n \u7ec4\u540e\u7b5b\u9009
\n order by
\n \u6392\u5e8f\u5b57\u6bb5 [asc | desc]
\n limit
\n \u8d77\u59cb\u7d22\u5f15, \u6570\u636e\u6761\u6570;
\n*\/<\/span>
\n# 1. \u521b\u5efa\u5546\u54c1\u8868.<\/span>
\ncreate<\/span> table<\/span> product
\n(<\/span>
\n pid int<\/span> primary<\/span> key<\/span> auto_increment<\/span>,<\/span> # \u5546\u54c1id, \u4e3b\u952e<\/span>
\n pname varchar<\/span>(<\/span>20<\/span>)<\/span>,<\/span> # \u5546\u54c1\u540d<\/span>
\n price double<\/span>,<\/span> # \u5546\u54c1\u5355\u4ef7<\/span>
\n category_id varchar<\/span>(<\/span>32<\/span>)<\/span> # \u5546\u54c1\u7684\u5206\u7c7bid<\/span>
\n)<\/span>;<\/span><\/p>\n

# 2. \u6dfb\u52a0\u8868\u6570\u636e.<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u8054\u60f3'<\/span>,<\/span>5000<\/span>,<\/span>'c001'<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u6d77\u5c14'<\/span>,<\/span>3000<\/span>,<\/span>'c001'<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u96f7\u795e'<\/span>,<\/span>5000<\/span>,<\/span>'c001'<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u6770\u514b\u743c\u65af'<\/span>,<\/span>800<\/span>,<\/span>'c002'<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u771f\u7ef4\u65af'<\/span>,<\/span>200<\/span>,<\/span> null<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u82b1\u82b1\u516c\u5b50'<\/span>,<\/span>440<\/span>,<\/span>'c002'<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u52b2\u9738'<\/span>,<\/span>2000<\/span>,<\/span>'c002'<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u9999\u5948\u513f'<\/span>,<\/span>800<\/span>,<\/span>'c003'<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u76f8\u5b9c\u672c\u8349'<\/span>,<\/span>200<\/span>,<\/span> null<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u9762\u9738'<\/span>,<\/span>5<\/span>,<\/span>'c003'<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u597d\u60f3\u4f60\u67a3'<\/span>,<\/span>56<\/span>,<\/span>'c004'<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u9999\u98d8\u98d8\u5976\u8336'<\/span>,<\/span>1<\/span>,<\/span>'c005'<\/span>)<\/span>;<\/span>
\nINSERT<\/span> INTO<\/span> product(<\/span>pid,<\/span>pname,<\/span>price,<\/span>category_id)<\/span> VALUES<\/span>(<\/span>null<\/span>,<\/span>'\u6d77\u6f9c\u4e4b\u5bb6'<\/span>,<\/span>1<\/span>,<\/span>'c002'<\/span>)<\/span>;<\/span><\/p>\n

# 3. \u67e5\u770b\u8868\u6570\u636e.<\/span>
\n# \u9700\u6c421: \u67e5\u8be2\u6240\u6709\u7684\u5546\u54c1\u4fe1\u606f<\/span>
\nselect<\/span> *<\/span> from<\/span> product;<\/span>
\nselect<\/span> pid,<\/span> pname,<\/span> price,<\/span> category_id from<\/span> product;<\/span> # \u6548\u679c\u540c\u4e0a.<\/span><\/p>\n

# \u9700\u6c422: \u67e5\u770b\u5546\u54c1\u540d \u548c \u5546\u54c1\u4ef7\u683c.<\/span>
\nselect<\/span> pname,<\/span> price from<\/span> product;<\/span>
\n# \u6269\u5c55: \u8d77\u522b\u540d, \u5217\u540d, \u8868\u540d\u90fd\u53ef\u4ee5\u8d77\u522b\u540d.<\/span>
\n# \u683c\u5f0f: \u5217\u540d as \u522b\u540d \u6216\u8005 \u8868\u540d as \u522b\u540d, \u5176\u4e2d as \u53ef\u4ee5\u7701\u7565\u4e0d\u5199.<\/span>
\nselect<\/span> pname as<\/span> \u5546\u54c1\u540d,<\/span> price \u5546\u54c1\u4ef7\u683c from<\/span> product as<\/span> p;<\/span><\/p>\n

# \u9700\u6c423: \u67e5\u770b\u7ed3\u679c\u662f\u8868\u8fbe\u5f0f, \u5c06\u6240\u6709\u7684\u5546\u54c1\u4ef7\u683c+10, \u8fdb\u884c\u5c55\u793a.<\/span>
\nselect<\/span> pname,<\/span> price +<\/span> 10<\/span> from<\/span> product;<\/span>
\nselect<\/span> pname,<\/span> price +<\/span> 10<\/span> as<\/span> price from<\/span> product;<\/span><\/p>\n

\u6761\u4ef6\u67e5\u8be2_\u6bd4\u8f83\u8fd0\u7b97\u7b26<\/h3>\n

# ——————— \u5355\u8868\u67e5\u8be2 -> \u6761\u4ef6\u67e5\u8be2 ———————<\/span>
\n# \u683c\u5f0f: select \u5217\u540d1, \u5217\u540d2… from \u6570\u636e\u8868\u540d where \u6761\u4ef6;<\/span>
\n# \u573a\u666f1: \u6bd4\u8f83\u8fd0\u7b97\u7b26, >, >=, <, <=, =, !=, <><\/span>
\n# \u9700\u6c421: \u67e5\u8be2\u5546\u54c1\u540d\u79f0\u4e3a\u201c\u82b1\u82b1\u516c\u5b50\u201d\u7684\u5546\u54c1\u6240\u6709\u4fe1\u606f：<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> pname =<\/span>'\u82b1\u82b1\u516c\u5b50'<\/span>;<\/span>
\n# \u9700\u6c422: \u67e5\u8be2\u4ef7\u683c\u4e3a800\u5546\u54c1<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> price=<\/span>800<\/span>;<\/span>
\n# \u9700\u6c423: \u67e5\u8be2\u4ef7\u683c\u4e0d\u662f800\u7684\u6240\u6709\u5546\u54c1<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> price!=<\/span>800<\/span>;<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> price<><\/span>800<\/span>;<\/span>
\n# \u9700\u6c424: \u67e5\u8be2\u5546\u54c1\u4ef7\u683c\u5927\u4e8e60\u5143\u7684\u6240\u6709\u5546\u54c1\u4fe1\u606f<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> price ><\/span> 60<\/span>;<\/span>
\n# \u9700\u6c425: \u67e5\u8be2\u5546\u54c1\u4ef7\u683c\u5c0f\u4e8e\u7b49\u4e8e800\u5143\u7684\u6240\u6709\u5546\u54c1\u4fe1\u606f<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> price <=<\/span> 800<\/span>;<\/span><\/p>\n

\u6761\u4ef6\u67e5\u8be2_\u903b\u8f91\u8fd0\u7b97\u7b26\u548c\u8303\u56f4\u67e5\u8be2<\/h3>\n

# \u573a\u666f2: \u8303\u56f4\u67e5\u8be2. between \u503c1 and \u503c2 -> \u9002\u7528\u4e8e\u8fde\u7eed\u7684\u533a\u95f4, in (\u503c1, \u503c2..) -> \u9002\u7528\u4e8e \u56fa\u5b9a\u503c\u7684\u5224\u65ad.<\/span>
\n# \u573a\u666f3: \u903b\u8f91\u8fd0\u7b97\u7b26. and, or, not<\/span>
\n# \u9700\u6c426: \u67e5\u8be2\u5546\u54c1\u4ef7\u683c\u5728200\u5230800\u4e4b\u95f4\u6240\u6709\u5546\u54c1<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> price between<\/span> 200<\/span> and<\/span> 800<\/span>;<\/span> # \u5305\u5de6\u5305\u53f3.<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> price >=<\/span> 200<\/span> and<\/span> price <=<\/span> 800<\/span>;<\/span><\/p>\n

# \u9700\u6c427: \u67e5\u8be2\u5546\u54c1\u4ef7\u683c\u662f200\u6216800\u7684\u6240\u6709\u5546\u54c1<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> price in<\/span> (<\/span>200<\/span>,<\/span> 800<\/span>)<\/span>;<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> price=<\/span>200<\/span> or<\/span> price=<\/span>800<\/span>;<\/span><\/p>\n

# \u9700\u6c428: \u67e5\u8be2\u4ef7\u683c\u4e0d\u662f800\u7684\u6240\u6709\u5546\u54c1<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> price !=<\/span> 800<\/span>;<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> not<\/span> price =<\/span> 800<\/span>;<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> price not<\/span> in<\/span> (<\/span>800<\/span>)<\/span>;<\/span><\/p>\n

\u6761\u4ef6\u5224\u65ad_\u6a21\u7cca\u67e5\u8be2\u548c\u975e\u7a7a\u5224\u65ad<\/h3>\n

# \u573a\u666f4: \u6a21\u7cca\u67e5\u8be2. \u5b57\u6bb5\u540d like '_\u5185\u5bb9%' _ \u4ee3\u8868\u4efb\u610f\u76841\u4e2a\u5b57\u7b26; %\u4ee3\u8868\u4efb\u610f\u7684\u591a\u4e2a\u5b57\u7b26, \u81f3\u5c110\u4e2a, \u81f3\u591a\u65e0\u6240\u8c13.<\/span>
\n# \u9700\u6c429: \u67e5\u8be2\u4ee5'\u9999'\u5f00\u5934\u7684\u6240\u6709\u5546\u54c1<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> pname like<\/span> '\u9999%'<\/span>;<\/span>
\n# \u9700\u6c4210: \u67e5\u8be2\u7b2c\u4e8c\u4e2a\u5b57\u4e3a'\u60f3'\u7684\u6240\u6709\u5546\u54c1<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> pname like<\/span> '_\u60f3%'<\/span>;<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> pname like<\/span> '_\u60f3'<\/span>;<\/span> # \u53ea\u80fd\u67e5\u51fa *\u60f3 \u4e24\u4e2a\u5b57\u7684, \u4e0d\u7b26\u5408\u9898\u8bbe.<\/span><\/p>\n

# \u573a\u666f5: \u975e\u7a7a\u67e5\u8be2. is null, is not null, \u4e0d\u80fd\u7528=\u6765\u5224\u65ad\u7a7a.<\/span>
\n# \u9700\u6c4211: \u67e5\u8be2\u6ca1\u6709\u5206\u7c7b\u7684\u5546\u54c1<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> category_id=<\/span>null<\/span>;<\/span> # \u4e0d\u62a5\u9519,\u4f46\u662f\u6ca1\u7ed3\u679c.<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> category_id is<\/span> null<\/span>;<\/span> # \u6b63\u786e\u7684, \u5224\u7a7a\u64cd\u4f5c.<\/span><\/p>\n

# \u9700\u6c4212: \u67e5\u8be2\u6709\u5206\u7c7b\u7684\u5546\u54c1<\/span>
\nselect<\/span> *<\/span> from<\/span> product where<\/span> category_id is<\/span> not<\/span> null<\/span>;<\/span> # \u6b63\u786e\u7684, \u975e\u7a7a\u5224\u65ad\u64cd\u4f5c.<\/span><\/p>\n

\u6392\u5e8f\u67e5\u8be2<\/h3>\n

# ——————— \u5355\u8868\u67e5\u8be2 -> \u6392\u5e8f\u67e5\u8be2 ———————<\/span>
\n# \u683c\u5f0f: select * from \u8868\u540d order by \u6392\u5e8f\u7684\u5b57\u6bb51 [asc | desc], \u6392\u5e8f\u7684\u5b57\u6bb52 [asc | desc], …;<\/span>
\n# \u89e3\u91ca1: ascending: \u5347\u5e8f, descending: \u964d\u5e8f.<\/span>
\n# \u89e3\u91ca2: \u9ed8\u8ba4\u662f\u5347\u5e8f, \u6240\u4ee5asc\u53ef\u4ee5\u7701\u7565\u4e0d\u5199.<\/span>
\n# \u9700\u6c421: \u6839\u636e\u4ef7\u683c\u964d\u5e8f\u6392\u5217.<\/span>
\nselect<\/span> *<\/span> from<\/span> product order<\/span> by<\/span> price;<\/span> # \u9ed8\u8ba4\u662f: \u5347\u5e8f.<\/span>
\nselect<\/span> *<\/span> from<\/span> product order<\/span> by<\/span> price asc<\/span>;<\/span> # \u6548\u679c\u540c\u4e0a.<\/span>
\nselect<\/span> *<\/span> from<\/span> product order<\/span> by<\/span> price desc<\/span>;<\/span> # \u4ef7\u683c\u964d\u5e8f\u6392\u5217.<\/span><\/p>\n

# \u9700\u6c422: \u6839\u636e\u4ef7\u683c\u964d\u5e8f\u6392\u5217, \u4ef7\u683c\u4e00\u6837\u7684\u60c5\u51b5\u4e0b, \u6839\u636e\u5206\u7c7b\u964d\u5e8f\u6392\u5217.<\/span>
\nselect<\/span> *<\/span> from<\/span> product order<\/span> by<\/span> price desc<\/span>,<\/span> category_id desc<\/span>;<\/span><\/p>\n

\u805a\u5408\u67e5\u8be2<\/h3>\n

\u805a\u5408\u67e5\u8be2(\u591a\u8fdb\u4e00\u51fa)\u4ecb\u7ecd:
\n\u6982\u8ff0:
\n\u805a\u5408\u67e5\u8be2\u662f\u5bf9\u8868\u4e2d\u7684\u67d0\u5217\u6570\u636e\u505a\u64cd\u4f5c.
\n\u5e38\u7528\u7684\u805a\u5408\u51fd\u6570:
\ncount() \u7edf\u8ba1\u67d0\u5217\u503c\u7684\u4e2a\u6570, \u53ea\u7edf\u8ba1\u975e\u7a7a\u503c. \u4e00\u822c\u7528\u4e8e\u7edf\u8ba1 \u8868\u4e2d\u6570\u636e\u7684\u603b\u6761\u6570.
\nsum() \u6c42\u548c
\nmax() \u6c42\u6700\u5927\u503c
\nmin() \u6c42\u6700\u5c0f\u503c
\navg() \u6c42\u5e73\u5747\u503c
\n\u9762\u8bd5\u9898: count(), count(1), count(\u5217)\u7684\u533a\u522b\u662f\u4ec0\u4e48?
\n\u533a\u522b1: \u662f\u5426\u7edf\u8ba1\u7a7a\u503c
\ncount(\u5217): \u53ea\u7edf\u8ba1\u8be5\u5217\u7684\u975e\u7a7a\u503c.
\ncount(1), count(): \u7edf\u8ba1\u6240\u6709\u6570\u636e, \u5305\u62ec\u7a7a\u503c.
\n\u533a\u522b2: \u6548\u7387\u95ee\u9898.
\n1. COUNT() \u548c COUNT(1) \u2014\u2014 \u6700\u5feb
\nInnoDB \u4f1a\u76f4\u63a5\u8bfb\u53d6\u805a\u7c07\u7d22\u5f15（PRIMARY KEY）\u7684\u884c\u6570\u8ba1\u6570\u5668（\u8fd1\u4f3c O(1)），\u65e0\u9700\u626b\u63cf\u6570\u636e\u9875\u3002
\n\u4f18\u5316\u5668\u5c06\u4e24\u8005\u89c6\u4e3a\u7b49\u4ef7，\u751f\u6210\u76f8\u540c\u6267\u884c\u8ba1\u5212\u3002
\n\u2705 \u63a8\u8350\u7528\u4e8e\u7edf\u8ba1\u603b\u884c\u6570\u3002
\n2. COUNT(\u4e3b\u952e\u5217) \u2014\u2014 \u6b21\u5feb
\n\u4e3b\u952e\u5217\u662f\u805a\u7c07\u7d22\u5f15\u7684\u4e00\u90e8\u5206，InnoDB \u53ef\u901a\u8fc7\u904d\u5386\u4e3b\u952e\u7d22\u5f15（B+\u6811\u53f6\u5b50\u8282\u70b9）\u8ba1\u6570\u3002
\n\u867d\u7136\u4ecd\u9700\u626b\u63cf\u7d22\u5f15\u9875，\u4f46\u907f\u514d\u56de\u8868，\u6bd4\u5168\u8868\u626b\u63cf\u5feb\u3002
\n\u26a0\ufe0f \u82e5\u4e3b\u952e\u662f\u8054\u5408\u4e3b\u952e\u6216\u975e\u6574\u578b，\u6027\u80fd\u7565\u4f4e\u4e8e COUNT()\u3002
\n3. COUNT(\u666e\u901a\u5217) \u2014\u2014 \u6700\u6162
\n\u82e5\u8be5\u5217\u65e0\u7d22\u5f15：\u9700\u5168\u8868\u626b\u63cf（type: ALL），\u9010\u884c\u5224\u65ad\u662f\u5426\u4e3a NULL\u3002
\n\u82e5\u8be5\u5217\u6709\u4e8c\u7ea7\u7d22\u5f15：\u53ef\u80fd\u8d70\u7d22\u5f15\u626b\u63cf（type: index），\u4f46\u4ecd\u9700\u8bbf\u95ee\u7d22\u5f15\u9875\u5e76\u8fc7\u6ee4 NULL\u3002
\n\u2757 \u5f53\u5217\u542b\u5927\u91cf NULL \u65f6，\u4f18\u5316\u5668\u65e0\u6cd5\u4f7f\u7528\u5143\u6570\u636e，\u5fc5\u987b\u5b9e\u9645\u8ba1\u7b97\u3002<\/p>\n

# ——————— \u5355\u8868\u67e5\u8be2 -> \u805a\u5408\u67e5\u8be2 ———————<\/span>
\n\/*
\n\u805a\u5408\u67e5\u8be2(\u591a\u8fdb\u4e00\u51fa)\u4ecb\u7ecd:
\n \u6982\u8ff0:
\n \u805a\u5408\u67e5\u8be2\u662f\u5bf9\u8868\u4e2d\u7684\u67d0\u5217\u6570\u636e\u505a\u64cd\u4f5c.
\n \u5e38\u7528\u7684\u805a\u5408\u51fd\u6570:
\n count() \u7edf\u8ba1\u67d0\u5217\u503c\u7684\u4e2a\u6570, \u53ea\u7edf\u8ba1\u975e\u7a7a\u503c. \u4e00\u822c\u7528\u4e8e\u7edf\u8ba1 \u8868\u4e2d\u6570\u636e\u7684\u603b\u6761\u6570.
\n sum() \u6c42\u548c
\n max() \u6c42\u6700\u5927\u503c
\n min() \u6c42\u6700\u5c0f\u503c
\n avg() \u6c42\u5e73\u5747\u503c
\n\u9762\u8bd5\u9898: count(*), count(1), count(\u5217)\u7684\u533a\u522b\u662f\u4ec0\u4e48?
\n \u533a\u522b1: \u662f\u5426\u7edf\u8ba1\u7a7a\u503c
\n count(\u5217): \u53ea\u7edf\u8ba1\u8be5\u5217\u7684\u975e\u7a7a\u503c.
\n count(1), count(*): \u7edf\u8ba1\u6240\u6709\u6570\u636e, \u5305\u62ec\u7a7a\u503c.
\n \u533a\u522b2: \u6548\u7387\u95ee\u9898.
\n 1. COUNT(*) \u548c COUNT(1) \u2014\u2014 \u6700\u5feb
\nInnoDB \u4f1a\u76f4\u63a5\u8bfb\u53d6\u805a\u7c07\u7d22\u5f15（PRIMARY KEY）\u7684\u884c\u6570\u8ba1\u6570\u5668（\u8fd1\u4f3c O(1)），\u65e0\u9700\u626b\u63cf\u6570\u636e\u9875\u3002
\n\u4f18\u5316\u5668\u5c06\u4e24\u8005\u89c6\u4e3a\u7b49\u4ef7，\u751f\u6210\u76f8\u540c\u6267\u884c\u8ba1\u5212\u3002
\n\u2705 \u63a8\u8350\u7528\u4e8e\u7edf\u8ba1\u603b\u884c\u6570\u3002
\n2. COUNT(\u4e3b\u952e\u5217) \u2014\u2014 \u6b21\u5feb
\n\u4e3b\u952e\u5217\u662f\u805a\u7c07\u7d22\u5f15\u7684\u4e00\u90e8\u5206，InnoDB \u53ef\u901a\u8fc7\u904d\u5386\u4e3b\u952e\u7d22\u5f15（B+\u6811\u53f6\u5b50\u8282\u70b9）\u8ba1\u6570\u3002
\n\u867d\u7136\u4ecd\u9700\u626b\u63cf\u7d22\u5f15\u9875，\u4f46\u907f\u514d\u56de\u8868，\u6bd4\u5168\u8868\u626b\u63cf\u5feb\u3002
\n\u26a0\ufe0f \u82e5\u4e3b\u952e\u662f\u8054\u5408\u4e3b\u952e\u6216\u975e\u6574\u578b，\u6027\u80fd\u7565\u4f4e\u4e8e COUNT(*)\u3002
\n3. COUNT(\u666e\u901a\u5217) \u2014\u2014 \u6700\u6162
\n\u82e5\u8be5\u5217\u65e0\u7d22\u5f15：\u9700\u5168\u8868\u626b\u63cf（type: ALL），\u9010\u884c\u5224\u65ad\u662f\u5426\u4e3a NULL\u3002
\n\u82e5\u8be5\u5217\u6709\u4e8c\u7ea7\u7d22\u5f15：\u53ef\u80fd\u8d70\u7d22\u5f15\u626b\u63cf（type: index），\u4f46\u4ecd\u9700\u8bbf\u95ee\u7d22\u5f15\u9875\u5e76\u8fc7\u6ee4 NULL\u3002
\n\u2757 \u5f53\u5217\u542b\u5927\u91cf NULL \u65f6，\u4f18\u5316\u5668\u65e0\u6cd5\u4f7f\u7528\u5143\u6570\u636e，\u5fc5\u987b\u5b9e\u9645\u8ba1\u7b97\u3002
\n*\/<\/span>
\n# \u9700\u6c421: \u67e5\u8be2\u5546\u54c1\u7684\u603b\u6761\u6570<\/span>
\nselect<\/span> count<\/span>(<\/span>pid)<\/span> as<\/span> total_cnt from<\/span> product;<\/span>
\nselect<\/span> count<\/span>(<\/span>category_id)<\/span> as<\/span> total_cnt from<\/span> product;<\/span>
\nselect<\/span> count<\/span>(<\/span>*<\/span>)<\/span> as<\/span> total_cnt from<\/span> product;<\/span>
\nselect<\/span> count<\/span>(<\/span>1<\/span>)<\/span> as<\/span> total_cnt from<\/span> product;<\/span><\/p>\n

# \u9700\u6c422: \u67e5\u8be2\u4ef7\u683c\u5927\u4e8e200\u5546\u54c1\u7684\u603b\u6761\u6570<\/span>
\nselect<\/span> count<\/span>(<\/span>pid)<\/span> as<\/span> total_cnt from<\/span> product where<\/span> price ><\/span> 200<\/span>;<\/span><\/p>\n

# \u9700\u6c423: \u67e5\u8be2\u5206\u7c7b\u4e3a'c001'\u7684\u6240\u6709\u5546\u54c1\u4ef7\u683c\u7684\u603b\u548c<\/span>
\nselect<\/span> sum<\/span>(<\/span>price)<\/span> as<\/span> total_price from<\/span> product where<\/span> category_id=<\/span>'c001'<\/span>;<\/span><\/p>\n

# \u9700\u6c424: \u67e5\u8be2\u5206\u7c7b\u4e3a'c002'\u6240\u6709\u5546\u54c1\u7684\u5e73\u5747\u4ef7\u683c<\/span>
\nselect<\/span> avg<\/span>(<\/span>price)<\/span> as<\/span> avg_price from<\/span> product where<\/span> category_id=<\/span>'c002'<\/span>;<\/span><\/p>\n

# \u9700\u6c425: \u67e5\u8be2\u5546\u54c1\u7684\u6700\u5927\u4ef7\u683c\u548c\u6700\u5c0f\u4ef7\u683c \u6269\u5c55: ctrl + alt + \u5b57\u6bcdL \u4ee3\u7801\u683c\u5f0f\u5316.<\/span>
\nselect<\/span>
\n max<\/span>(<\/span>price)<\/span> as<\/span> max_price,<\/span>
\n min<\/span>(<\/span>price)<\/span> as<\/span> min_price
\nfrom<\/span>
\n product;<\/span><\/p>\n

\u5206\u7ec4\u67e5\u8be2<\/h3>\n

\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\"<\/p>\n

\u5206\u7ec4\u67e5\u8be2\u4ecb\u7ecd:
\n\u6982\u8ff0:
\n\u7b80\u5355\u7406\u89e3\u4e3a, \u6839\u636e\u5206\u7ec4\u5b57\u6bb5, \u628a\u8868\u6570\u636e \u5316\u6574\u4e3a\u96f6, \u7136\u540e\u57fa\u4e8e\u6bcf\u4e2a\u5206\u7ec4\u540e\u7684\u6bcf\u4e2a\u90e8\u5206, \u8fdb\u884c\u5bf9\u5e94\u7684\u805a\u5408\u8fd0\u7b97.
\n\u683c\u5f0f:
\nselect \u52171, \u52172\u2026 from \u6570\u636e\u8868\u540d where \u7ec4\u524d\u7b5b\u9009 group by \u5206\u7ec4\u5b57\u6bb5 having \u7ec4\u540e\u7b5b\u9009;
\n\u7ec6\u8282:
\n1. \u5206\u7ec4\u67e5\u8be2 \u4e00\u822c\u8981\u7ed3\u5408 \u805a\u5408\u51fd\u6570\u4e00\u8d77\u4f7f\u7528, \u4e14\u6839\u636e\u8c01\u5206\u7ec4, \u5c31\u6839\u636e\u8c01\u67e5\u8be2.
\n2. \u7ec4\u524d\u7b5b\u9009\u7528where, \u7ec4\u540e\u7b5b\u9009\u7528having.
\n3. \u9762\u8bd5\u9898: where \u548c having\u7684\u533a\u522b\u662f\u4ec0\u4e48?
\nwhere: \u7ec4\u524d\u7b5b\u9009, \u540e\u8fb9\u4e0d\u80fd\u8ddf\u805a\u5408\u51fd\u6570.
\nhaving: \u7ec4\u540e\u7b5b\u9009, \u540e\u8fb9\u53ef\u4ee5\u8ddf\u805a\u5408\u51fd\u6570.
\n4. \u5206\u7ec4\u67e5\u8be2\u7684\u67e5\u8be2\u5217 \u53ea\u80fd\u51fa\u73b0 \u5206\u7ec4\u5b57\u6bb5, \u805a\u5408\u51fd\u6570.
\n5. \u5982\u679c\u53ea\u5206\u7ec4, \u6ca1\u6709\u5199\u805a\u5408, \u53ef\u4ee5\u7406\u89e3\u4e3a\u662f: \u57fa\u4e8e\u5206\u7ec4\u5b57\u6bb5, \u8fdb\u884c\u53bb\u91cd\u67e5\u8be2<\/p>\n

# ——————— \u5355\u8868\u67e5\u8be2 -> \u5206\u7ec4\u67e5\u8be2 ———————<\/span>
\n\/*
\n\u5206\u7ec4\u67e5\u8be2\u4ecb\u7ecd:
\n \u6982\u8ff0:
\n \u7b80\u5355\u7406\u89e3\u4e3a, \u6839\u636e\u5206\u7ec4\u5b57\u6bb5, \u628a\u8868\u6570\u636e \u5316\u6574\u4e3a\u96f6, \u7136\u540e\u57fa\u4e8e\u6bcf\u4e2a\u5206\u7ec4\u540e\u7684\u6bcf\u4e2a\u90e8\u5206, \u8fdb\u884c\u5bf9\u5e94\u7684\u805a\u5408\u8fd0\u7b97.
\n \u683c\u5f0f:
\n select \u52171, \u52172… from \u6570\u636e\u8868\u540d where \u7ec4\u524d\u7b5b\u9009 group by \u5206\u7ec4\u5b57\u6bb5 having \u7ec4\u540e\u7b5b\u9009;
\n \u7ec6\u8282:
\n 1. \u5206\u7ec4\u67e5\u8be2 \u4e00\u822c\u8981\u7ed3\u5408 \u805a\u5408\u51fd\u6570\u4e00\u8d77\u4f7f\u7528, \u4e14\u6839\u636e\u8c01\u5206\u7ec4, \u5c31\u6839\u636e\u8c01\u67e5\u8be2.
\n 2. \u7ec4\u524d\u7b5b\u9009\u7528where, \u7ec4\u540e\u7b5b\u9009\u7528having.
\n 3. \u9762\u8bd5\u9898: where \u548c having\u7684\u533a\u522b\u662f\u4ec0\u4e48?
\n where: \u7ec4\u524d\u7b5b\u9009, \u540e\u8fb9\u4e0d\u80fd\u8ddf\u805a\u5408\u51fd\u6570.
\n having: \u7ec4\u540e\u7b5b\u9009, \u540e\u8fb9\u53ef\u4ee5\u8ddf\u805a\u5408\u51fd\u6570.
\n 4. \u5206\u7ec4\u67e5\u8be2\u7684\u67e5\u8be2\u5217 \u53ea\u80fd\u51fa\u73b0 \u5206\u7ec4\u5b57\u6bb5, \u805a\u5408\u51fd\u6570.
\n 5. \u5982\u679c\u53ea\u5206\u7ec4, \u6ca1\u6709\u5199\u805a\u5408, \u53ef\u4ee5\u7406\u89e3\u4e3a\u662f: \u57fa\u4e8e\u5206\u7ec4\u5b57\u6bb5, \u8fdb\u884c\u53bb\u91cd\u67e5\u8be2
\n *\/<\/span>
\n# \u9700\u6c421: \u7edf\u8ba1\u5404\u4e2a\u5206\u7c7b\u5546\u54c1\u7684\u4e2a\u6570.<\/span>
\nselect<\/span> category_id,<\/span> count<\/span>(<\/span>*<\/span>)<\/span> as<\/span> total_cnt from<\/span> product group<\/span> by<\/span> category_id;<\/span><\/p>\n

# \u9700\u6c422: \u7edf\u8ba1\u5404\u4e2a\u5206\u7c7b\u5546\u54c1\u7684\u4e2a\u6570, \u4e14\u53ea\u663e\u793a\u4e2a\u6570\u5927\u4e8e1\u7684\u4fe1\u606f.<\/span>
\nselect<\/span>
\n category_id,<\/span>
\n count<\/span>(<\/span>*<\/span>)<\/span> as<\/span> total_cnt
\nfrom<\/span>
\n product
\ngroup<\/span> by<\/span>
\n category_id # \u6839\u636e\u5546\u54c1\u7c7b\u522b\u5206\u7ec4.<\/span>
\nhaving<\/span>
\n total_cnt ><\/span> 1<\/span>;<\/span> # \u7ec4\u540e\u7b5b\u9009<\/span><\/p>\n

# \u9700\u6c423: \u6f14\u793a \u5982\u679c\u53ea\u5206\u7ec4, \u6ca1\u6709\u5199\u805a\u5408, \u53ef\u4ee5\u7406\u89e3\u4e3a\u662f: \u57fa\u4e8e\u5206\u7ec4\u5b57\u6bb5, \u8fdb\u884c\u53bb\u91cd\u67e5\u8be2<\/span>
\nselect<\/span> category_id from<\/span> product group<\/span> by<\/span> category_id;<\/span>
\nselect<\/span> category_id from<\/span> product group<\/span> by<\/span> category_id;<\/span><\/p>\n

# \u8fd8\u53ef\u4ee5\u901a\u8fc7 distinct \u5173\u952e\u5b57\u6765\u5b9e\u73b0\u53bb\u91cd.<\/span>
\nselect<\/span> distinct<\/span> category_id from<\/span> product;<\/span><\/p>\n

# \u6b64\u65f6\u662f: \u6309\u7167category_id \u548c price\u4f5c\u4e3a\u6574\u4f53, \u7136\u540e\u53bb\u91cd.<\/span>
\nselect<\/span> distinct<\/span> category_id,<\/span> price from<\/span> product;<\/span>
\nselect<\/span> category_id,<\/span> price from<\/span> product group<\/span> by<\/span> category_id,<\/span> price;<\/span> # \u6548\u679c\u540c\u4e0a.<\/span><\/p>\n

\u5206\u9875\u67e5\u8be2<\/h3>\n

\u5206\u9875\u67e5\u8be2\u4ecb\u7ecd:
\n\u6982\u8ff0:
\n\u5206\u9875\u67e5\u8be2 = \u6bcf\u6b21\u4ece\u6570\u636e\u8868\u4e2d\u67e5\u8be2\u51fa\u56fa\u5b9a\u6761\u6570\u7684\u6570\u636e, \u4e00\u65b9\u9762\u53ef\u4ee5\u964d\u4f4e\u670d\u52a1\u5668\u7684\u538b\u529b, \u53e6\u4e00\u65b9\u9762\u53ef\u4ee5\u964d\u4f4e\u6d4f\u89c8\u5668\u7aef\u7684\u538b\u529b, \u4e14\u53ef\u4ee5\u63d0\u9ad8\u7528\u6237\u4f53\u9a8c.
\n\u5b9e\u9645\u5f00\u53d1\u4e2d\u975e\u5e38\u5e38\u7528.
\n\u683c\u5f0f:
\nlimit \u8d77\u59cb\u7d22\u5f15, \u6570\u636e\u6761\u6570;
\n\u7ec6\u8282:
\n1. \u8868\u4e2d\u6bcf\u6761\u6570\u636e\u90fd\u6709\u81ea\u5df1\u7684\u7d22\u5f15, \u4e14\u7d22\u5f15\u662f\u4ece0\u5f00\u59cb\u7684.
\n2. \u5982\u679c\u662f\u4ece\u7d22\u5f150\u5f00\u59cb\u83b7\u53d6\u6570\u636e\u7684, \u5219\u7d22\u5f150\u53ef\u4ee5\u7701\u7565\u4e0d\u5199.
\n\u5b66\u597d\u5206\u9875, \u638c\u63e1\u5982\u4e0b\u7684\u51e0\u4e2a\u53c2\u6570\u8ba1\u7b97\u89c4\u5219\u5373\u53ef:
\n\u6570\u636e\u603b\u6761\u6570: count() \u51fd\u6570
\n\u6bcf\u9875\u7684\u6570\u636e\u6761\u6570: \u4ea7\u54c1\u8bf4\u4e86\u7b97
\n\u6bcf\u9875\u7684\u8d77\u59cb\u7d22\u5f15: (\u5f53\u524d\u7684\u9875\u6570 – 1) * \u6bcf\u9875\u7684\u6570\u636e\u6761\u6570
\n\u603b\u9875\u6570: (\u6570\u636e\u603b\u6761\u6570 + \u6bcf\u9875\u7684\u6570\u636e\u6761\u6570 – 1) \/\/ \u6bcf\u9875\u7684\u6570\u636e\u6761\u6570
\n(13 + 5 – 1) \/\/ 5 = 17 \/\/ 5 = 3\u9875
\n(14 + 5 – 1) \/\/ 5 = 18 \/\/ 5 = 3\u9875
\n(15 + 5 – 1) \/\/ 5 = 19 \/\/ 5 = 3\u9875
\n(16 + 5 – 1) \/\/ 5 = 20 \/\/ 5 = 4\u9875<\/p>\n

# ——————— \u5355\u8868\u67e5\u8be2 -> \u5206\u9875\u67e5\u8be2 ———————<\/span>
\n\/*
\n\u5206\u9875\u67e5\u8be2\u4ecb\u7ecd:
\n \u6982\u8ff0:
\n \u5206\u9875\u67e5\u8be2 = \u6bcf\u6b21\u4ece\u6570\u636e\u8868\u4e2d\u67e5\u8be2\u51fa\u56fa\u5b9a\u6761\u6570\u7684\u6570\u636e, \u4e00\u65b9\u9762\u53ef\u4ee5\u964d\u4f4e\u670d\u52a1\u5668\u7684\u538b\u529b, \u53e6\u4e00\u65b9\u9762\u53ef\u4ee5\u964d\u4f4e\u6d4f\u89c8\u5668\u7aef\u7684\u538b\u529b, \u4e14\u53ef\u4ee5\u63d0\u9ad8\u7528\u6237\u4f53\u9a8c.
\n \u5b9e\u9645\u5f00\u53d1\u4e2d\u975e\u5e38\u5e38\u7528.
\n \u683c\u5f0f:
\n limit \u8d77\u59cb\u7d22\u5f15, \u6570\u636e\u6761\u6570;
\n \u7ec6\u8282:
\n 1. \u8868\u4e2d\u6bcf\u6761\u6570\u636e\u90fd\u6709\u81ea\u5df1\u7684\u7d22\u5f15, \u4e14\u7d22\u5f15\u662f\u4ece0\u5f00\u59cb\u7684.
\n 2. \u5982\u679c\u662f\u4ece\u7d22\u5f150\u5f00\u59cb\u83b7\u53d6\u6570\u636e\u7684, \u5219\u7d22\u5f150\u53ef\u4ee5\u7701\u7565\u4e0d\u5199.
\n \u5b66\u597d\u5206\u9875, \u638c\u63e1\u5982\u4e0b\u7684\u51e0\u4e2a\u53c2\u6570\u8ba1\u7b97\u89c4\u5219\u5373\u53ef:
\n \u6570\u636e\u603b\u6761\u6570: count() \u51fd\u6570
\n \u6bcf\u9875\u7684\u6570\u636e\u6761\u6570: \u4ea7\u54c1\u8bf4\u4e86\u7b97
\n \u6bcf\u9875\u7684\u8d77\u59cb\u7d22\u5f15: (\u5f53\u524d\u7684\u9875\u6570 – 1) * \u6bcf\u9875\u7684\u6570\u636e\u6761\u6570
\n \u603b\u9875\u6570: (\u6570\u636e\u603b\u6761\u6570 + \u6bcf\u9875\u7684\u6570\u636e\u6761\u6570 – 1) \/\/ \u6bcf\u9875\u7684\u6570\u636e\u6761\u6570
\n (13 + 5 – 1) \/\/ 5 = 17 \/\/ 5 = 3\u9875
\n (14 + 5 – 1) \/\/ 5 = 18 \/\/ 5 = 3\u9875
\n (15 + 5 – 1) \/\/ 5 = 19 \/\/ 5 = 3\u9875
\n (16 + 5 – 1) \/\/ 5 = 20 \/\/ 5 = 4\u9875
\n*\/<\/span>
\n# \u9700\u6c421: 5\u6761\/\u9875.<\/span>
\nselect<\/span> *<\/span> from<\/span> product limit<\/span> 5<\/span>;<\/span> # \u7b2c1\u9875, \u4ece\u7d22\u5f150\u5f00\u59cb, \u83b7\u53d65\u6761.<\/span>
\nselect<\/span> *<\/span> from<\/span> product limit<\/span> 0<\/span>,<\/span> 5<\/span>;<\/span> # \u7b2c1\u9875, \u4ece\u7d22\u5f150\u5f00\u59cb, \u83b7\u53d65\u6761, \u6548\u679c\u540c\u4e0a.<\/span><\/p>\n

select<\/span> *<\/span> from<\/span> product limit<\/span> 0<\/span>,<\/span> 5<\/span>;<\/span> # \u7b2c1\u9875, \u4ece\u7d22\u5f150\u5f00\u59cb, \u83b7\u53d65\u6761.<\/span>
\nselect<\/span> *<\/span> from<\/span> product limit<\/span> 5<\/span>,<\/span> 5<\/span>;<\/span> # \u7b2c2\u9875, \u4ece\u7d22\u5f155\u5f00\u59cb, \u83b7\u53d65\u6761.<\/span><\/p>\n

# \u9700\u6c422: 3\u6761\/\u9875<\/span>
\nselect<\/span> *<\/span> from<\/span> product limit<\/span> 0<\/span>,<\/span> 3<\/span>;<\/span> # \u7b2c1\u9875, \u4ece\u7d22\u5f150\u5f00\u59cb, \u83b7\u53d63\u6761.<\/span>
\nselect<\/span> *<\/span> from<\/span> product limit<\/span> 3<\/span>,<\/span> 3<\/span>;<\/span> # \u7b2c2\u9875, \u4ece\u7d22\u5f153\u5f00\u59cb, \u83b7\u53d63\u6761.<\/span>
\nselect<\/span> *<\/span> from<\/span> product limit<\/span> 6<\/span>,<\/span> 3<\/span>;<\/span> # \u7b2c3\u9875, \u4ece\u7d22\u5f156\u5f00\u59cb, \u83b7\u53d63\u6761.<\/span>
\nselect<\/span> *<\/span> from<\/span> product limit<\/span> 9<\/span>,<\/span> 3<\/span>;<\/span> # \u7b2c4\u9875, \u4ece\u7d22\u5f159\u5f00\u59cb, \u83b7\u53d63\u6761.<\/span>
\nselect<\/span> *<\/span> from<\/span> product limit<\/span> 12<\/span>,<\/span> 3<\/span>;<\/span> # \u7b2c5\u9875, \u4ece\u7d22\u5f1512\u5f00\u59cb, \u83b7\u53d63\u6761.<\/span><\/p>\n

# \u603b\u7ed3, \u56de\u987e\u5355\u8868\u67e5\u8be2\u7684\u683c\u5f0f<\/span>
\n\/*
\nselect
\n [distinct] \u52171 as \u522b\u540d, \u52172
\nfrom
\n \u6570\u636e\u8868\u540d
\nwhere
\n \u7ec4\u524d\u7b5b\u9009
\ngroup by
\n \u5206\u7ec4\u5b57\u6bb5
\nhaving
\n \u7ec4\u540e\u7b5b\u9009
\norder by
\n \u6392\u5e8f\u5b57\u6bb5 [asc | desc]
\nlimit
\n \u8d77\u59cb\u7d22\u5f15, \u6570\u636e\u6761\u6570;
\n*\/<\/span>
\n# \u9700\u6c42: \u7edf\u8ba1\u5546\u54c1\u8868\u4e2d, \u6bcf\u7c7b\u5546\u54c1\u7684\u5355\u4ef7\u603b\u548c, \u53ea\u7edf\u8ba1\u5355\u4ef7\u5728100\u4ee5\u4e0a\u7684\u5546\u54c1, \u53ea\u67e5\u770b\u5355\u4ef7\u603b\u548c\u5728500\u4ee5\u4e0a\u7684\u5206\u7c7b, \u6309\u7167\u5546\u54c1\u603b\u4ef7\u964d\u5e8f\u6392\u5217, \u53ea\u83b7\u53d6\u5546\u54c1\u603b\u4ef7\u9ad8\u7684\u524d2\u6761\u6570\u4fe1\u606f.<\/span>
\nselect<\/span>
\n category_id,<\/span>
\n sum<\/span>(<\/span>price)<\/span> total_price
\nfrom<\/span>
\n product
\nwhere<\/span> # \u7ec4\u524d\u7b5b\u9009<\/span>
\n price ><\/span> 100<\/span>
\ngroup<\/span> by<\/span> # \u5206\u7ec4<\/span>
\n category_id
\nhaving<\/span> # \u7ec4\u540e\u7b5b\u9009<\/span>
\n total_price ><\/span> 500<\/span>
\norder<\/span> by<\/span> # \u6392\u5e8f<\/span>
\n total_price desc<\/span>
\nlimit<\/span> 0<\/span>,<\/span> 2<\/span>;<\/span> # \u5206\u9875<\/span><\/p>\n

\u591a\u8868\u5efa\u8868_\u4e00\u5bf9\u591a<\/h3>\n