{"id":113709,"date":"2026-10-07T08:17:41","date_gmt":"2026-10-07T00:17:41","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/113709.html"},"modified":"2026-10-07T08:17:41","modified_gmt":"2026-10-07T00:17:41","slug":"sql-%e5%9f%ba%e7%a1%80%e7%bb%bc%e5%90%88%e7%bb%83%e4%b9%a0%ef%bc%9a%e5%ad%a6%e7%94%9f%e6%88%90%e7%bb%a9%e8%a1%a8%e4%b8%8e%e8%ae%a2%e5%8d%95%e8%a1%a8-30-%e9%a2%98","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/113709.html","title":{"rendered":"SQL \u57fa\u7840\u7efc\u5408\u7ec3\u4e60\uff1a\u5b66\u751f\u6210\u7ee9\u8868\u4e0e\u8ba2\u5355\u8868 30 \u9898"},"content":{"rendered":"

\u6211\u521a\u5b66 SQL \u90a3\u4f1a，\u80cc\u4e86\u4e24\u5468\u8bed\u6cd5，\u4e00\u53e5"\u67e5\u6210\u7ee9\u4e3a\u7a7a\u7684\u5b66\u751f"\u5c31\u628a\u6211\u5361\u4f4f\u2014\u2014\u6211\u7406\u6240\u5f53\u7136\u5730\u5199\u4e86 WHERE score = NULL，\u7ed3\u679c\u4e00\u884c\u90fd\u67e5\u4e0d\u5230，\u56e0\u4e3a\u7a7a\u503c（NULL）\u6839\u672c\u4e0d\u80fd\u7528\u7b49\u53f7\u6bd4\u8f83\u3002<\/p>\n\n\u8d44\u6e90\u94fe\u63a5<\/tr>\n\n\n\n
SQL \u7ec3\u4e60\u6587\u4ef6<\/td>\n\u70b9\u51fb\u67e5\u770b<\/td>\n<\/tr>\n
\u8fd9\u7bc7\u7528\u5b66\u751f\u6210\u7ee9\u8868\u548c\u8ba2\u5355\u8868\u4e24\u6761\u4e3b\u7ebf\u300130 \u9053\u9012\u8fdb\u7ec3\u4e60，\u5e26\u4f60\u628a\u96f6\u6563\u8bed\u6cd5\u7ec3\u6210"\u770b\u61c2\u9700\u6c42 \u2192 \u62c6\u5f00\u6b65\u9aa4 \u2192 \u5199\u7a33\u8bed\u53e5"\u7684\u56fa\u5b9a\u624b\u611f\u3002<\/td>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\"\"<\/p>\n

\u4e00\u3001\u7ec3\u4e60\u6570\u636e：\u5148\u628a\u4e24\u5f20\u8868\u6446\u4e0a\u684c<\/h3>\n

\u540e\u9762\u6240\u6709\u9898\u76ee\u90fd\u56f4\u7ed5\u4e24\u5f20\u4e1a\u52a1\u8868\u5c55\u5f00，\u5b57\u6bb5\u5148\u5bf9\u9f50\u3002<\/p>\n

\u5b66\u751f\u6210\u7ee9\u8868 student_score<\/p>\n\n\u5b57\u6bb5\u542b\u4e49<\/tr>\n\n\n\n\n\n\n\n
student_id<\/td>\n\u5b66\u53f7<\/td>\n<\/tr>\n
student_name<\/td>\n\u59d3\u540d<\/td>\n<\/tr>\n
class_name<\/td>\n\u73ed\u7ea7<\/td>\n<\/tr>\n
course_name<\/td>\n\u8bfe\u7a0b<\/td>\n<\/tr>\n
score<\/td>\n\u6210\u7ee9<\/td>\n<\/tr>\n
exam_date<\/td>\n\u8003\u8bd5\u65e5\u671f<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u8ba2\u5355\u8868 orders<\/p>\n\n\u5b57\u6bb5\u542b\u4e49<\/tr>\n\n\n\n\n\n\n\n\n\n\n
order_id<\/td>\n\u8ba2\u5355\u53f7<\/td>\n<\/tr>\n
customer_id<\/td>\n\u5ba2\u6237\u7f16\u53f7<\/td>\n<\/tr>\n
customer_name<\/td>\n\u5ba2\u6237\u59d3\u540d<\/td>\n<\/tr>\n
product_name<\/td>\n\u5546\u54c1\u540d\u79f0<\/td>\n<\/tr>\n
category<\/td>\n\u5546\u54c1\u7c7b\u522b<\/td>\n<\/tr>\n
quantity<\/td>\n\u6570\u91cf<\/td>\n<\/tr>\n
price<\/td>\n\u5355\u4ef7<\/td>\n<\/tr>\n
order_date<\/td>\n\u4e0b\u5355\u65e5\u671f<\/td>\n<\/tr>\n
city<\/td>\n\u57ce\u5e02<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u4e8c\u3001\u57fa\u7840\u67e5\u8be2：\u5148\u628a\u6570\u636e\u635e\u51c6<\/h3>\n

\u8981\u5206\u6790\u6570\u636e，\u5148\u5f97\u628a\u6570\u636e\u4ece\u8868\u91cc\u635e\u51fa\u6765\u3002\u53ef\u540c\u6837\u662f"\u67e5"，\u4e3a\u4ec0\u4e48\u4f60\u5199\u7684\u8bed\u53e5\u8981\u4e48\u67e5\u591a\u4e86\u884c，\u8981\u4e48\u6f0f\u6389\u4e86\u672c\u8be5\u6709\u7684\u8bb0\u5f55？<\/p>\n\n\u9898\u53f7\u4e1a\u52a1\u9700\u6c42\u5173\u952e\u5199\u6cd5<\/tr>\n\n\n\n\n\n\n\n
1<\/td>\n\u67e5\u6240\u6709\u5b66\u751f\u7684\u59d3\u540d\u3001\u8bfe\u7a0b\u3001\u6210\u7ee9<\/td>\nSELECT \u6295\u5f71\u5217<\/td>\n<\/tr>\n
2<\/td>\n\u67e5\u6210\u7ee9 \u2265 90 \u7684\u8bb0\u5f55<\/td>\nWHERE + \u6bd4\u8f83\u7b26<\/td>\n<\/tr>\n
3<\/td>\n\u67e5\u4e00\u73ed\u4e14\u6210\u7ee9\u5728 80\u201390<\/td>\nAND + BETWEEN<\/td>\n<\/tr>\n
4<\/td>\n\u67e5\u6570\u5b66\u6216\u82f1\u8bed\u8bfe\u7a0b<\/td>\nIN<\/td>\n<\/tr>\n
5<\/td>\n\u67e5\u59d3\u540d\u4e2d\u5e26"\u5f20"<\/td>\nLIKE \u6a21\u7cca\u5339\u914d<\/td>\n<\/tr>\n
6<\/td>\n\u67e5\u6210\u7ee9\u4e3a\u7a7a\u7684\u8bb0\u5f55<\/td>\nIS NULL<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u7b2c 1 \u9898：\u67e5\u8be2\u6240\u6709\u5b66\u751f\u7684\u59d3\u540d\u3001\u8bfe\u7a0b\u548c\u6210\u7ee9<\/h4>\n

SELECT<\/span> student_name,<\/span> course_name,<\/span> score
\nFROM<\/span> student_score;<\/span><\/p>\n

\u53ea\u53d6\u9700\u8981\u7684\u5217，\u4e0d\u7528 SELECT *，\u907f\u514d\u62d6\u56de\u65e0\u5173\u6570\u636e\u3002<\/p>\n

\u7b2c 2 \u9898：\u67e5\u8be2\u6210\u7ee9\u5927\u4e8e\u7b49\u4e8e 90 \u5206\u7684\u8bb0\u5f55<\/h4>\n

SELECT<\/span> *<\/span>
\nFROM<\/span> student_score
\nWHERE<\/span> score >=<\/span> 90<\/span>;<\/span><\/p>\n

\u7b2c 3 \u9898：\u67e5\u8be2\u73ed\u7ea7\u4e3a"\u4e00\u73ed"\u4e14\u6210\u7ee9\u5728 80 \u5230 90 \u4e4b\u95f4\u7684\u5b66\u751f<\/h4>\n

SELECT<\/span> student_name,<\/span> course_name,<\/span> score
\nFROM<\/span> student_score
\nWHERE<\/span> class_name =<\/span> '\u4e00\u73ed'<\/span>
\n AND<\/span> score BETWEEN<\/span> 80<\/span> AND<\/span> 90<\/span>;<\/span><\/p>\n

BETWEEN … AND … \u5305\u542b\u4e24\u7aef\u8fb9\u754c，\u5199\u6210 > 80 AND < 90 \u4f1a\u628a 80 \u548c 90 \u6f0f\u6389\u3002<\/p>\n

\u7b2c 4 \u9898：\u67e5\u8be2\u8bfe\u7a0b\u4e3a"\u6570\u5b66"\u6216"\u82f1\u8bed"\u7684\u6210\u7ee9\u8bb0\u5f55<\/h4>\n

SELECT<\/span> *<\/span>
\nFROM<\/span> student_score
\nWHERE<\/span> course_name IN<\/span> (<\/span>'\u6570\u5b66'<\/span>,<\/span> '\u82f1\u8bed'<\/span>)<\/span>;<\/span><\/p>\n

\u679a\u4e3e\u79bb\u6563\u503c\u7528 IN，\u6bd4\u4e00\u8fde\u4e32 OR \u66f4\u6e05\u723d\u3002<\/p>\n

\u7b2c 5 \u9898：\u67e5\u8be2\u59d3\u540d\u4e2d\u5305\u542b"\u5f20"\u7684\u5b66\u751f<\/h4>\n

SELECT<\/span> *<\/span>
\nFROM<\/span> student_score
\nWHERE<\/span> student_name LIKE<\/span> '%\u5f20%'<\/span>;<\/span><\/p>\n

% \u4ee3\u8868\u4efb\u610f\u591a\u4e2a\u5b57\u7b26，_ \u4ee3\u8868\u5355\u4e2a\u5b57\u7b26\u3002<\/p>\n

\u7b2c 6 \u9898：\u67e5\u8be2\u6210\u7ee9\u4e3a\u7a7a\u7684\u5b66\u751f\u8bb0\u5f55<\/h4>\n

SELECT<\/span> *<\/span>
\nFROM<\/span> student_score
\nWHERE<\/span> score IS<\/span> NULL<\/span>;<\/span><\/p>\n

\u9519\u8bef：<font style="color:#c00;">WHERE score = NULL<\/font> \u4e00\u884c\u90fd\u67e5\u4e0d\u5230，NULL \u4e0e\u4efb\u4f55\u503c\u7684\u6bd4\u8f83\u7ed3\u679c\u90fd\u4e0d\u662f"\u771f"\u3002<\/p>\n

\u6b63\u786e：\u5224\u7a7a\u53ea\u80fd\u7528 <font style="color:#080;">IS NULL<\/font>，\u975e\u7a7a\u7528 <font style="color:#080;">IS NOT NULL<\/font>\u3002<\/p>\n

\u4e09\u3001\u6392\u5e8f\u805a\u5408：\u4ece\u9010\u884c\u8bb0\u5f55\u5230\u4e00\u4e2a\u6c47\u603b\u6570\u5b57<\/h3>\n

\u6570\u636e\u635e\u51fa\u6765\u4e86，\u53ef\u4e00\u5806\u65e0\u5e8f\u884c\u6ca1\u6cd5\u770b，\u9700\u6c42\u8fd8\u60f3\u8981"\u6570\u5b66\u5e73\u5747\u5206"\u201c\u591a\u5c11\u4e2a\u72ec\u7acb\u5ba2\u6237\u201d\u3002\u4ece\u9010\u884c\u8bb0\u5f55\u8de8\u5230\u4e00\u4e2a\u6c47\u603b\u6570\u5b57，\u8fd9\u4e00\u6b65\u600e\u4e48\u5199？<\/p>\n\n\u9898\u53f7\u4e1a\u52a1\u9700\u6c42\u5173\u952e\u5199\u6cd5<\/tr>\n\n\n\n\n\n\n\n
7<\/td>\n\u6210\u7ee9\u4ece\u9ad8\u5230\u4f4e\u6392\u5217<\/td>\nORDER BY … DESC<\/td>\n<\/tr>\n
8<\/td>\n\u73ed\u7ea7\u5347\u5e8f\u3001\u6210\u7ee9\u964d\u5e8f<\/td>\n\u591a\u5b57\u6bb5\u6392\u5e8f<\/td>\n<\/tr>\n
9<\/td>\n\u5217\u51fa\u6240\u6709\u51fa\u73b0\u8fc7\u7684\u8bfe\u7a0b<\/td>\nDISTINCT<\/td>\n<\/tr>\n
10<\/td>\n\u7edf\u8ba1\u603b\u8bb0\u5f55\u6570<\/td>\nCOUNT(*)<\/td>\n<\/tr>\n
11<\/td>\n\u6570\u5b66\u7684\u5e73\u5747\/\u6700\u9ad8\/\u6700\u4f4e\u5206<\/td>\nAVG\/MAX\/MIN<\/td>\n<\/tr>\n
12<\/td>\n\u7edf\u8ba1\u4e0d\u540c\u5ba2\u6237\u7684\u6570\u91cf<\/td>\nCOUNT(DISTINCT …)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u7b2c 7 \u9898：\u6309\u6210\u7ee9\u4ece\u9ad8\u5230\u4f4e\u67e5\u8be2<\/h4>\n

SELECT<\/span> student_name,<\/span> course_name,<\/span> score
\nFROM<\/span> student_score
\nORDER<\/span> BY<\/span> score DESC<\/span>;<\/span><\/p>\n

\u7b2c 8 \u9898：\u6309\u73ed\u7ea7\u5347\u5e8f\u3001\u6210\u7ee9\u964d\u5e8f\u6392\u5217<\/h4>\n

SELECT<\/span> class_name,<\/span> student_name,<\/span> score
\nFROM<\/span> student_score
\nORDER<\/span> BY<\/span> class_name ASC<\/span>,<\/span> score DESC<\/span>;<\/span><\/p>\n

\u524d\u4e00\u4e2a\u5b57\u6bb5\u503c\u76f8\u540c，\u624d\u4f1a\u8f6e\u5230\u540e\u4e00\u4e2a\u5b57\u6bb5\u6392\u5e8f\u3002<\/p>\n

\u7b2c 9 \u9898：\u67e5\u8be2\u6240\u6709\u51fa\u73b0\u8fc7\u7684\u8bfe\u7a0b\u540d\u79f0\u5e76\u53bb\u91cd<\/h4>\n

SELECT<\/span> DISTINCT<\/span> course_name
\nFROM<\/span> student_score;<\/span><\/p>\n

\u7b2c 10 \u9898：\u7edf\u8ba1\u6210\u7ee9\u8868\u7684\u603b\u8bb0\u5f55\u6570<\/h4>\n

SELECT<\/span> COUNT<\/span>(<\/span>*<\/span>)<\/span> AS<\/span> total_rows
\nFROM<\/span> student_score;<\/span><\/p>\n

\u7b2c 11 \u9898：\u7edf\u8ba1\u6570\u5b66\u8bfe\u7a0b\u7684\u5e73\u5747\u5206\u3001\u6700\u9ad8\u5206\u3001\u6700\u4f4e\u5206<\/h4>\n

SELECT<\/span> AVG<\/span>(<\/span>score)<\/span> AS<\/span> avg_score,<\/span>
\n MAX<\/span>(<\/span>score)<\/span> AS<\/span> max_score,<\/span>
\n MIN<\/span>(<\/span>score)<\/span> AS<\/span> min_score
\nFROM<\/span> student_score
\nWHERE<\/span> course_name =<\/span> '\u6570\u5b66'<\/span>;<\/span><\/p>\n

COUNT(*) \u7edf\u8ba1\u5168\u90e8\u884c\u6570，COUNT(\u5217) \u53ea\u7edf\u8ba1\u8be5\u5217\u975e\u7a7a\u7684\u884c\u6570；\u805a\u5408\u51fd\u6570\u4f1a\u81ea\u52a8\u5ffd\u7565\u7a7a\u503c\u3002<\/p>\n

\u7b2c 12 \u9898：\u7edf\u8ba1\u8ba2\u5355\u8868\u4e2d\u4e0d\u540c\u5ba2\u6237\u7684\u6570\u91cf<\/h4>\n

SELECT<\/span> COUNT<\/span>(<\/span>DISTINCT<\/span> customer_id)<\/span> AS<\/span> customer_count
\nFROM<\/span> orders;<\/span><\/p>\n

\u53bb\u91cd\u540e\u518d\u8ba1\u6570，\u8fd9\u6b63\u662f"\u72ec\u7acb\u5ba2\u6237\u6570"\u7684\u6807\u51c6\u5199\u6cd5\u3002<\/p>\n

\u6ce8\u610f：\u5148\u8fc7\u6ee4\u3001\u518d\u805a\u5408，WHERE \u6c38\u8fdc\u8dd1\u5728\u805a\u5408\u51fd\u6570\u524d\u9762\u3002<\/p>\n

\u56db\u3001\u5206\u7ec4\u7edf\u8ba1：\u4e00\u884c SQL \u7b97\u51fa\u591a\u7ec4\u7ed3\u679c<\/h3>\n

\u5168\u5c40\u4e00\u4e2a\u5e73\u5747\u5206\u597d\u7b97，\u53ef\u9700\u6c42\u662f"\u6bcf\u4e2a\u73ed\u3001\u6bcf\u95e8\u8bfe\u3001\u6bcf\u4e2a\u5ba2\u6237"\u5404\u81ea\u7684\u6570\u5b57，\u600e\u4e48\u8ba9\u4e00\u6761\u8bed\u53e5\u540c\u65f6\u5410\u51fa\u591a\u7ec4\u7ed3\u679c？<\/p>\n\n\u9898\u53f7\u4e1a\u52a1\u9700\u6c42\u5173\u952e\u5199\u6cd5<\/tr>\n\n\n\n\n\n\n\n
13<\/td>\n\u7edf\u8ba1\u6bcf\u4e2a\u73ed\u7684\u4eba\u6570<\/td>\nGROUP BY<\/td>\n<\/tr>\n
14<\/td>\n\u7edf\u8ba1\u6bcf\u95e8\u8bfe\u7684\u5e73\u5747\u5206<\/td>\n\u5206\u7ec4 + AVG<\/td>\n<\/tr>\n
15<\/td>\n\u6bcf\u4e2a\u73ed\u6bcf\u95e8\u8bfe\u7684\u5e73\u5747\u5206<\/td>\n\u591a\u5b57\u6bb5\u5206\u7ec4<\/td>\n<\/tr>\n
16<\/td>\n\u5e73\u5747\u5206\u5927\u4e8e 85 \u7684\u8bfe\u7a0b<\/td>\nHAVING<\/td>\n<\/tr>\n
17<\/td>\n\u6bcf\u4e2a\u5ba2\u6237\u7684\u8ba2\u5355\u603b\u91d1\u989d<\/td>\n\u5206\u7ec4 + SUM<\/td>\n<\/tr>\n
18<\/td>\n\u603b\u91d1\u989d\u8d85 1000 \u7684\u5ba2\u6237<\/td>\n\u5206\u7ec4\u540e\u8fc7\u6ee4<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u7b2c 13 \u9898：\u7edf\u8ba1\u6bcf\u4e2a\u73ed\u7ea7\u7684\u5b66\u751f\u4eba\u6570<\/h4>\n

SELECT<\/span> class_name,<\/span> COUNT<\/span>(<\/span>*<\/span>)<\/span> AS<\/span> student_count
\nFROM<\/span> student_score
\nGROUP<\/span> BY<\/span> class_name;<\/span><\/p>\n

\u7b2c 14 \u9898：\u7edf\u8ba1\u6bcf\u95e8\u8bfe\u7a0b\u7684\u5e73\u5747\u5206<\/h4>\n

SELECT<\/span> course_name,<\/span> AVG<\/span>(<\/span>score)<\/span> AS<\/span> avg_score
\nFROM<\/span> student_score
\nGROUP<\/span> BY<\/span> course_name;<\/span><\/p>\n

\u7b2c 15 \u9898：\u7edf\u8ba1\u6bcf\u4e2a\u73ed\u7ea7\u6bcf\u95e8\u8bfe\u7a0b\u7684\u5e73\u5747\u5206<\/h4>\n

SELECT<\/span> class_name,<\/span> course_name,<\/span> AVG<\/span>(<\/span>score)<\/span> AS<\/span> avg_score
\nFROM<\/span> student_score
\nGROUP<\/span> BY<\/span> class_name,<\/span> course_name;<\/span><\/p>\n

\u591a\u5b57\u6bb5\u5206\u7ec4\u7684\u7c92\u5ea6\u662f\u5b57\u6bb5\u7ec4\u5408，\u5148\u6309\u73ed\u7ea7\u3001\u518d\u6309\u8bfe\u7a0b\u5207\u5206\u3002<\/p>\n

\u7b2c 16 \u9898：\u67e5\u8be2\u5e73\u5747\u5206\u5927\u4e8e 85 \u7684\u8bfe\u7a0b<\/h4>\n

SELECT<\/span> course_name,<\/span> AVG<\/span>(<\/span>score)<\/span> AS<\/span> avg_score
\nFROM<\/span> student_score
\nGROUP<\/span> BY<\/span> course_name
\nHAVING<\/span> AVG<\/span>(<\/span>score)<\/span> ><\/span> 85<\/span>;<\/span><\/p>\n

\u6211\u5728\u8fd9\u513f\u683d\u8fc7：\u628a\u805a\u5408\u6761\u4ef6\u5199\u8fdb <font style="color:#c00;">WHERE AVG(score) > 85<\/font>，\u8bed\u53e5\u76f4\u63a5\u62a5\u9519\u3002<\/p>\n

\u7b2c 17 \u9898：\u7edf\u8ba1\u6bcf\u4e2a\u5ba2\u6237\u7684\u8ba2\u5355\u603b\u91d1\u989d<\/h4>\n

SELECT<\/span> customer_id,<\/span> customer_name,<\/span>
\n SUM<\/span>(<\/span>quantity *<\/span> price)<\/span> AS<\/span> total_amount
\nFROM<\/span> orders
\nGROUP<\/span> BY<\/span> customer_id,<\/span> customer_name;<\/span><\/p>\n

\u7b2c 18 \u9898：\u67e5\u8be2\u8ba2\u5355\u603b\u91d1\u989d\u8d85\u8fc7 1000 \u7684\u5ba2\u6237<\/h4>\n

SELECT<\/span> customer_id,<\/span> customer_name,<\/span>
\n SUM<\/span>(<\/span>quantity *<\/span> price)<\/span> AS<\/span> total_amount
\nFROM<\/span> orders
\nGROUP<\/span> BY<\/span> customer_id,<\/span> customer_name
\nHAVING<\/span> SUM<\/span>(<\/span>quantity *<\/span> price)<\/span> ><\/span> 1000<\/span>;<\/span><\/p>\n

\u884c\u8fc7\u6ee4\u4e0e\u7ec4\u8fc7\u6ee4\u5230\u5e95\u5dee\u5728\u54ea？\u770b\u6570\u636e\u5e93\u7684\u903b\u8f91\u6267\u884c\u987a\u5e8f：<\/p>\n

FROM \u2192 WHERE \u2192 GROUP BY \u2192 HAVING \u2192 SELECT \u2192 ORDER BY \u2192 LIMIT<\/p>\n

WHERE \u5728\u5206\u7ec4\u524d\u9010\u884c\u8fc7\u6ee4，\u624b\u91cc\u6839\u672c\u6ca1\u6709\u805a\u5408\u7ed3\u679c；HAVING \u5728\u5206\u7ec4\u540e\u6267\u884c，\u4e13\u95e8\u7b5b\u9009\u805a\u5408\u503c\u3002<\/p>\n

\u8bb0\u4f4f：WHERE \u8fc7\u6ee4\u884c，HAVING \u8fc7\u6ee4\u7ec4，\u805a\u5408\u6761\u4ef6\u53ea\u80fd\u8fdb HAVING\u3002<\/p>\n

\u4e94\u3001\u8fde\u63a5\u5b50\u67e5\u8be2：\u8de8\u8868\u62fc\u5b57\u6bb5\u3001\u5206\u6b65\u7b97\u7ed3\u679c<\/h3>\n

\u5355\u8868\u80fd\u67e5\u7684\u90fd\u67e5\u5b8c\u4e86，\u53ef\u4fe1\u606f\u6563\u843d\u5728\u591a\u5f20\u8868，\u8fd8\u5f97\u56de\u7b54"\u8c01\u6ca1\u4e0b\u8fc7\u5355""\u54ea\u5355\u91d1\u989d\u6700\u9ad8"\u8fd9\u7c7b\u9700\u8981\u5148\u7b97\u4e00\u6b65\u7684\u95ee\u9898，\u8fd9\u65f6\u5019\u600e\u4e48\u529e？<\/p>\n\n\u9898\u53f7\u4e1a\u52a1\u9700\u6c42\u5173\u952e\u5199\u6cd5<\/tr>\n\n\n\n\n\n\n\n
19<\/td>\n\u53d6\u5b66\u751f\u59d3\u540d\u3001\u8bfe\u7a0b\u3001\u6210\u7ee9\u3001\u73ed\u7ea7<\/td>\n\u5355\u8868\u76f4\u67e5（\u5bf9\u6bd4）<\/td>\n<\/tr>\n
20<\/td>\n\u53d6\u8ba2\u5355\u7684\u5ba2\u6237\u3001\u5546\u54c1\u4fe1\u606f<\/td>\n\u5355\u8868\u76f4\u67e5（\u5bf9\u6bd4）<\/td>\n<\/tr>\n
21<\/td>\n\u67e5\u6bcf\u4e2a\u73ed\u7ea7\u7684\u73ed\u4e3b\u4efb<\/td>\nJOIN … ON<\/td>\n<\/tr>\n
22<\/td>\n\u67e5\u6ca1\u4e0b\u8fc7\u8ba2\u5355\u7684\u5ba2\u6237<\/td>\nNOT IN \u5b50\u67e5\u8be2<\/td>\n<\/tr>\n
23<\/td>\n\u67e5\u91d1\u989d\u6700\u9ad8\u7684\u8ba2\u5355<\/td>\n\u6807\u91cf\u5b50\u67e5\u8be2<\/td>\n<\/tr>\n
24<\/td>\n\u67e5\u5ba2\u6237\u603b\u91d1\u989d\u5e76\u5e26\u59d3\u540d<\/td>\n\u5206\u7ec4（\u8fde\u63a5\u53ef\u6269\u5c55）<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u7b2c 19 \u9898：\u67e5\u8be2\u5b66\u751f\u59d3\u540d\u3001\u8bfe\u7a0b\u3001\u6210\u7ee9\u5e76\u663e\u793a\u73ed\u7ea7<\/h4>\n

SELECT<\/span> student_name,<\/span> class_name,<\/span> course_name,<\/span> score
\nFROM<\/span> student_score;<\/span><\/p>\n

\u5b57\u6bb5\u90fd\u5728\u4e00\u5f20\u8868，\u76f4\u63a5\u67e5\u5373\u53ef，\u4e0d\u5fc5\u4e3a\u4e86\u8fde\u63a5\u800c\u8fde\u63a5\u3002<\/p>\n

\u7b2c 20 \u9898：\u67e5\u8be2\u6bcf\u4e2a\u8ba2\u5355\u7684\u5ba2\u6237\u59d3\u540d\u548c\u5546\u54c1\u540d\u79f0<\/h4>\n

SELECT<\/span> order_id,<\/span> customer_name,<\/span> product_name,<\/span> quantity,<\/span> price
\nFROM<\/span> orders;<\/span><\/p>\n

\u7b2c 21 \u9898：\u5047\u8bbe\u6709\u73ed\u7ea7\u8868 class_info(class_name, teacher_name)，\u67e5\u6bcf\u4e2a\u73ed\u7684\u73ed\u4e3b\u4efb<\/h4>\n

SELECT<\/span> s.<\/span>student_name,<\/span> s.<\/span>class_name,<\/span> c.<\/span>teacher_name
\nFROM<\/span> student_score s
\nJOIN<\/span> class_info c
\n ON<\/span> s.<\/span>class_name =<\/span> c.<\/span>class_name;<\/span><\/p>\n

\u8fde\u63a5（JOIN）\u6309\u5173\u8054\u5b57\u6bb5\u62fc\u8868，\u5173\u8054\u6761\u4ef6\u5199\u5728 ON \u4e4b\u540e\u3002\u6211\u6f0f\u5199\u8fc7\u4e00\u6b21 ON，\u76f4\u63a5\u62fc\u51fa\u7b1b\u5361\u5c14\u79ef（Cartesian Product），\u884c\u6570\u53d8\u6210\u4e24\u8868\u76f8\u4e58，\u6d4b\u8bd5\u5e93\u5f53\u573a\u5361\u4f4f\u3002<\/p>\n

\u7b2c 22 \u9898：\u67e5\u8be2\u6ca1\u6709\u4e0b\u8fc7\u8ba2\u5355\u7684\u5ba2\u6237<\/h4>\n

SELECT<\/span> customer_id,<\/span> customer_name
\nFROM<\/span> customers
\nWHERE<\/span> customer_id NOT<\/span> IN<\/span> (<\/span>
\n SELECT<\/span> DISTINCT<\/span> customer_id
\n FROM<\/span> orders
\n)<\/span>;<\/span><\/p>\n

\u5907\u6ce8：customers \u4e3a\u5ba2\u6237\u4e3b\u8868\u3002\u5f53\u5b50\u67e5\u8be2\u7ed3\u679c\u91cc\u6df7\u5165 NULL \u65f6，<font style="color:#666;">NOT IN<\/font> \u4f1a\u6574\u4f53\u5931\u6548；\u66f4\u7a33\u7684\u5199\u6cd5\u662f <font style="color:#666;">NOT EXISTS<\/font>\u3002<\/p>\n

SELECT<\/span> c.<\/span>customer_id,<\/span> c.<\/span>customer_name
\nFROM<\/span> customers c
\nWHERE<\/span> NOT<\/span> EXISTS<\/span> (<\/span>
\n SELECT<\/span> 1<\/span>
\n FROM<\/span> orders o
\n WHERE<\/span> o.<\/span>customer_id =<\/span> c.<\/span>customer_id
\n)<\/span>;<\/span><\/p>\n

\u7b2c 23 \u9898：\u67e5\u8be2\u8ba2\u5355\u91d1\u989d\u6700\u9ad8\u7684\u8ba2\u5355\u4fe1\u606f<\/h4>\n

SELECT<\/span> *<\/span>
\nFROM<\/span> orders
\nWHERE<\/span> quantity *<\/span> price =<\/span> (<\/span>
\n SELECT<\/span> MAX<\/span>(<\/span>quantity *<\/span> price)<\/span>
\n FROM<\/span> orders
\n)<\/span>;<\/span><\/p>\n

\u5b50\u67e5\u8be2（Subquery）\u8fd4\u56de\u5355\u4e2a\u503c\u65f6\u7528 = \u6bd4\u8f83；\u8fd4\u56de\u591a\u4e2a\u503c\u8981\u7528 IN\u3001ANY \u6216 ALL\u3002<\/p>\n

\u7b2c 24 \u9898：\u67e5\u8be2\u6bcf\u4e2a\u5ba2\u6237\u7684\u8ba2\u5355\u603b\u91d1\u989d\u5e76\u5217\u51fa\u59d3\u540d<\/h4>\n

SELECT<\/span> o.<\/span>customer_id,<\/span>
\n o.<\/span>customer_name,<\/span>
\n SUM<\/span>(<\/span>o.<\/span>quantity *<\/span> o.<\/span>price)<\/span> AS<\/span> total_amount
\nFROM<\/span> orders o
\nGROUP<\/span> BY<\/span> o.<\/span>customer_id,<\/span> o.<\/span>customer_name;<\/span><\/p>\n

\u9700\u8981\u8865\u5ba2\u6237\u8d44\u6599\u65f6，\u5148\u6309\u5ba2\u6237\u805a\u5408，\u518d\u8fde\u63a5\u5ba2\u6237\u8868\u8865\u5b57\u6bb5\u3002<\/p>\n

\u6ce8\u610f：\u8fde\u63a5\u62fc\u5b57\u6bb5，\u5b50\u67e5\u8be2\u5206\u6b65\u7b97，\u590d\u6742\u67e5\u8be2\u4ece\u5185\u5c42\u5f80\u5916\u5199\u3002<\/p>\n

\u516d\u3001\u66f4\u65b0\u5efa\u8868：\u5199\u64cd\u4f5c\u7684\u7a33\u59a5\u843d\u5730\u4e0e TopN<\/h3>\n

\u53ea\u8bfb\u6570\u636e\u4e0d\u591f，\u4f60\u8fd8\u8981\u6539\u6570\u636e\u3001\u5efa\u8868\u3001\u63d2\u8bb0\u5f55，\u5e76\u7ed9\u51fa"\u6d88\u8d39 Top 3 \u5ba2\u6237"\u3002\u5199\u64cd\u4f5c\u4e00\u65e6\u51fa\u9519，\u540e\u679c\u6bd4\u67e5\u8be2\u91cd\u5f97\u591a，\u600e\u4e48\u7a33\u59a5\u843d\u5730？<\/p>\n\n\u9898\u53f7\u4e1a\u52a1\u9700\u6c42\u5173\u952e\u5199\u6cd5<\/tr>\n\n\n\n\n\n\n\n
25<\/td>\n\u6570\u5b66\u4e0d\u53ca\u683c\u7684\u6210\u7ee9\u52a0 5 \u5206<\/td>\nUPDATE<\/td>\n<\/tr>\n
26<\/td>\n\u5220\u9664\u6210\u7ee9\u4e3a\u7a7a\u7684\u8bb0\u5f55<\/td>\nDELETE<\/td>\n<\/tr>\n
27<\/td>\n\u65b0\u5efa\u5b66\u751f\u6210\u7ee9\u8868<\/td>\nCREATE TABLE<\/td>\n<\/tr>\n
28<\/td>\n\u63d2\u5165\u4e00\u6761\u8ba2\u5355\u8bb0\u5f55<\/td>\nINSERT<\/td>\n<\/tr>\n
29<\/td>\n\u5404\u57ce\u5e02\u603b\u91d1\u989d\u964d\u5e8f<\/td>\n\u5206\u7ec4 + \u6392\u5e8f<\/td>\n<\/tr>\n
30<\/td>\n\u603b\u91d1\u989d\u524d 3 \u7684\u5ba2\u6237<\/td>\nLIMIT \u53d6 TopN<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u7b2c 25 \u9898：\u5c06\u6570\u5b66\u8bfe\u7a0b\u4e2d\u4f4e\u4e8e 60 \u5206\u7684\u6210\u7ee9\u7edf\u4e00\u52a0 5 \u5206<\/h4>\n

UPDATE<\/span> student_score
\nSET<\/span> score =<\/span> score +<\/span> 5<\/span>
\nWHERE<\/span> course_name =<\/span> '\u6570\u5b66'<\/span>
\n AND<\/span> score <<\/span> 60<\/span>;<\/span><\/p>\n

\u7b2c 26 \u9898：\u5220\u9664\u6210\u7ee9\u4e3a\u7a7a\u7684\u5b66\u751f\u8bb0\u5f55<\/h4>\n

DELETE<\/span> FROM<\/span> student_score
\nWHERE<\/span> score IS<\/span> NULL<\/span>;<\/span><\/p>\n

\u6211\u89c1\u8fc7\u6700\u75bc\u7684\u4e8b\u6545：<font style="color:#c00;">UPDATE<\/font>\u3001<font style="color:#c00;">DELETE<\/font> \u6f0f\u6389 <font style="color:#c00;">WHERE<\/font>，\u6574\u8868\u88ab\u6539\u4e14\u9ed8\u8ba4\u65e0\u6cd5\u64a4\u9500\u3002<\/p>\n

\u505a\u6cd5：\u5148\u628a <font style="color:#080;">WHERE<\/font> \u6761\u4ef6\u5957\u8fdb <font style="color:#080;">SELECT<\/font> \u8dd1\u4e00\u904d，\u786e\u8ba4\u547d\u4e2d\u7684\u884c\u65e0\u8bef，\u518d\u6267\u884c\u6539\u5199\u3002<\/p>\n

\u7b2c 27 \u9898：\u65b0\u5efa\u4e00\u5f20\u5b66\u751f\u6210\u7ee9\u8868<\/h4>\n

CREATE<\/span> TABLE<\/span> student_score (<\/span>
\n student_id INT<\/span>,<\/span>
\n student_name VARCHAR<\/span>(<\/span>50<\/span>)<\/span>,<\/span>
\n class_name VARCHAR<\/span>(<\/span>50<\/span>)<\/span>,<\/span>
\n course_name VARCHAR<\/span>(<\/span>50<\/span>)<\/span>,<\/span>
\n score DECIMAL<\/span>(<\/span>5<\/span>,<\/span>2<\/span>)<\/span>,<\/span>
\n exam_date DATE<\/span>
\n)<\/span>;<\/span><\/p>\n

\u6574\u6570\u7528 INT\u3001\u5b57\u7b26\u4e32\u7528 VARCHAR\u3001\u5c0f\u6570\u7528 DECIMAL\u3001\u65e5\u671f\u7528 DATE\u3002<\/p>\n

\u7b2c 28 \u9898：\u5411\u8ba2\u5355\u8868\u63d2\u5165\u4e00\u6761\u8ba2\u5355\u8bb0\u5f55<\/h4>\n

INSERT<\/span> INTO<\/span> orders (<\/span>
\n order_id,<\/span> customer_id,<\/span> customer_name,<\/span>
\n product_name,<\/span> category,<\/span> quantity,<\/span>
\n price,<\/span> order_date,<\/span> city
\n)<\/span> VALUES<\/span> (<\/span>
\n 1001<\/span>,<\/span> 1<\/span>,<\/span> '\u5f20\u4e09'<\/span>,<\/span>
\n '\u7b14\u8bb0\u672c'<\/span>,<\/span> '\u6570\u7801'<\/span>,<\/span> 2<\/span>,<\/span>
\n 5999.00<\/span>,<\/span> '2024-06-01'<\/span>,<\/span> '\u5317\u4eac'<\/span>
\n)<\/span>;<\/span><\/p>\n

\u5b57\u6bb5\u987a\u5e8f\u4e0e\u503c\u987a\u5e8f\u5fc5\u987b\u4e00\u4e00\u5bf9\u5e94\u3002<\/p>\n

\u7b2c 29 \u9898：\u67e5\u8be2\u6bcf\u4e2a\u57ce\u5e02\u7684\u8ba2\u5355\u603b\u91d1\u989d，\u5e76\u6309\u91d1\u989d\u964d\u5e8f<\/h4>\n

SELECT<\/span> city,<\/span> SUM<\/span>(<\/span>quantity *<\/span> price)<\/span> AS<\/span> total_amount
\nFROM<\/span> orders
\nGROUP<\/span> BY<\/span> city
\nORDER<\/span> BY<\/span> total_amount DESC<\/span>;<\/span><\/p>\n

\u7b2c 30 \u9898：\u67e5\u8be2\u8ba2\u5355\u603b\u91d1\u989d\u6392\u540d\u524d 3 \u7684\u5ba2\u6237<\/h4>\n

SELECT<\/span> customer_id,<\/span> customer_name,<\/span>
\n SUM<\/span>(<\/span>quantity *<\/span> price)<\/span> AS<\/span> total_amount
\nFROM<\/span> orders
\nGROUP<\/span> BY<\/span> customer_id,<\/span> customer_name
\nORDER<\/span> BY<\/span> total_amount DESC<\/span>
\nLIMIT<\/span> 3<\/span>;<\/span><\/p>\n

\u5907\u6ce8：<font style="color:#666;">LIMIT<\/font> \u4e3a MySQL\/PostgreSQL \u5199\u6cd5；SQL Server \u7528 <font style="color:#666;">TOP<\/font>，Oracle \u7528 <font style="color:#666;">FETCH FIRST n ROWS ONLY<\/font>\u3002<\/p>\n

\u6ce8\u610f：\u5148\u67e5\u540e\u6539，UPDATE\/DELETE \u4e0d\u5e26 WHERE \u5c31\u662f\u4e8b\u6545\u3002<\/p>\n

\u4e03\u3001\u603b\u7ed3<\/h3>\n

30 \u9898\u8d70\u4e0b\u6765，\u4e00\u6761\u4e3b\u7ebf\u5f88\u6e05\u695a：\u5b66\u751f\u6210\u7ee9\u8868\u7ec3\u7684\u662f\u8fc7\u6ee4\u3001\u805a\u5408\u4e0e\u5206\u7ec4，\u8ba2\u5355\u8868\u7ec3\u7684\u662f\u4e1a\u52a1\u8ba1\u7b97\u3001\u8fde\u63a5\u4e0e\u6392\u5e8f，\u5199\u64cd\u4f5c\u5219\u903c\u7740\u4f60\u517b\u6210"\u5148\u67e5\u540e\u6539"\u7684\u4e60\u60ef\u3002<\/p>\n

\u60f3\u628a\u624b\u611f\u56fa\u5316，\u518d\u505a\u4e09\u4ef6\u4e8b：<\/p>\n

    \n
  • \u628a\u6210\u7ee9\u6539\u6210 59\u300160\u300161 \u8fd9\u7c7b\u8fb9\u754c\u503c\u91cd\u8dd1，\u4f53\u4f1a BETWEEN \u4e0e > \u7684\u5dee\u5f02；<\/li>\n
  • \u540c\u4e00\u9898\u7528 NOT IN\u3001NOT EXISTS\u3001LEFT JOIN \u4e09\u79cd\u5199\u6cd5\u5404\u5199\u4e00\u904d；<\/li>\n
  • \u6bcf\u6761 SQL \u90fd\u6309\u6267\u884c\u987a\u5e8f\u590d\u76d8\u4e00\u6b21，\u8bf4\u6e05\u6bcf\u4e00\u6b65\u7684\u5148\u540e\u3002<\/li>\n<\/ul>\n

    \u8bed\u6cd5\u8bb0\u4e0d\u4f4f\u53ef\u4ee5\u968f\u65f6\u67e5，\u601d\u8def\u9519\u4e86\u624d\u4f1a\u6b65\u6b65\u9519\u3002\u628a\u8fd9\u6761\u9012\u8fdb\u94fe\u8def\u7ec3\u719f，\u518d\u53bb\u78b0\u7a97\u53e3\u51fd\u6570\u3001CTE \u548c\u7d22\u5f15\u4f18\u5316，\u4f1a\u987a\u5f88\u591a\u3002<\/p>\n

    \"\"<\/p>\n

    \u672f\u8bed\u901f\u67e5\u8868<\/h4>\n\n\u672f\u8bed\u82f1\u6587 \/ \u5173\u952e\u5b57\u542b\u4e49<\/tr>\n\n\n\n\n\n\n\n\n\n\n
    \u7a7a\u503c<\/td>\nNULL<\/td>\n\u672a\u77e5\u6216\u7f3a\u5931\u503c，\u53ea\u80fd\u7528 IS NULL \u5224\u65ad<\/td>\n<\/tr>\n
    \u8c13\u8bcd<\/td>\nPredicate<\/td>\nWHERE \u540e\u8fd4\u56de\u771f\/\u5047\u7684\u6761\u4ef6\u8868\u8fbe\u5f0f<\/td>\n<\/tr>\n
    \u805a\u5408\u51fd\u6570<\/td>\nAggregate Function<\/td>\n\u5bf9\u4e00\u7ec4\u884c\u8ba1\u7b97\u51fa\u5355\u4e2a\u503c<\/td>\n<\/tr>\n
    \u5206\u7ec4<\/td>\nGROUP BY<\/td>\n\u6309\u5b57\u6bb5\u628a\u6570\u636e\u5212\u5206\u4e3a\u591a\u4e2a\u7ec4<\/td>\n<\/tr>\n
    \u8fde\u63a5<\/td>\nJOIN<\/td>\n\u6309\u5173\u8054\u6761\u4ef6\u62fc\u5408\u591a\u5f20\u8868<\/td>\n<\/tr>\n
    \u5b50\u67e5\u8be2<\/td>\nSubquery<\/td>\n\u5d4c\u5957\u5728\u53e6\u4e00\u6761\u8bed\u53e5\u4e2d\u7684\u67e5\u8be2<\/td>\n<\/tr>\n
    \u7b1b\u5361\u5c14\u79ef<\/td>\nCartesian Product<\/td>\n\u591a\u8868\u65e0\u6761\u4ef6\u914d\u5bf9，\u884c\u6570\u76f8\u4e58<\/td>\n<\/tr>\n
    \u522b\u540d<\/td>\nAlias<\/td>\n\u7528 AS \u7ed9\u8868\u6216\u5217\u8d77\u7684\u4e34\u65f6\u540d<\/td>\n<\/tr>\n
    \u5206\u9875<\/td>\nPagination<\/td>\n\u7528 LIMIT \u5206\u6bb5\u8fd4\u56de\u7ed3\u679c<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    \u53c2\u8003\u94fe\u63a5<\/h4>\n
      \n
    • MySQL 8.0 Reference Manual \u2014 SELECT Statement<\/li>\n
    • MySQL 8.0 Reference Manual \u2014 Aggregate Functions<\/li>\n
    • MySQL 8.0 Reference Manual \u2014 JOIN Syntax<\/li>\n
    • MySQL 8.0 Reference Manual \u2014 UPDATE Syntax<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"

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