\u4e00\u4e2a\u5b57\u6bb5\u5982\u679c\u6ca1\u6709\u88ab\u660e\u786e\u8d4b\u503c，\u5b83\u5c06\u9ed8\u8ba4\u4e3aNULL<\/span>\u3002
\n2. \u67e5\u8be2NULL\u503c<\/p>\n\u8981\u67e5\u8be2NULL\u503c，\u53ef\u4ee5\u4f7f\u7528IS NULL\u6761\u4ef6\u3002\u4f8b\u5982，\u5982\u679c\u627e\u51fa\u67d0\u4e2a\u8868\u4e2d\u6240\u6709NULL\u503c\u7684\u884c，\u53ef\u4ee5\u8fd9\u6837\u5199：
\nSELECT * FROM your_table WHERE your_column IS NULL;<\/p>\n
3. \u67e5\u8be2\u975eNULL\u503c<\/p>\n
\u5982\u679c\u67e5\u8be2\u975eNULL\u503c\u7684\u884c，\u53ef\u4ee5\u4f7f\u7528IS NOT NULL\u6761\u4ef6：
\nSELECT * FROM your_table WHERE your_column IS NOT NULL;<\/p>\n
4. \u4f7f\u7528NVL\u51fd\u6570\u5904\u7406NULL\u503c<\/p>\n
NVL\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u5c06NULL\u503c\u66ff\u6362\u4e3a\u6307\u5b9a\u7684\u503c\u3002\u8fd9\u5bf9\u4e8e\u5728\u663e\u793a\u6216\u8ba1\u7b97\u65f6\u5904\u7406NULL\u503c\u5f88\u6709\u7528\u3002\u4f8b\u5982：
\nSELECT NVL(your_column, '\u66ff\u4ee3\u503c') FROM your_table;<\/p>\n
\u8fd9\u5c06\u628ayour_column\u4e2d\u7684\u6240\u6709NULL\u503c\u66ff\u6362\u4e3a\u5b57\u7b26\u4e32'\u66ff\u4ee3\u503c'\u3002
\n5. \u4f7f\u7528COALESCE\u51fd\u6570<\/p>\n
COALESCE\u51fd\u6570\u8fd4\u56de\u53c2\u6570\u5217\u8868\u4e2d\u7684\u7b2c\u4e00\u4e2a\u975eNULL\u503c\u3002\u8fd9\u5728\u4ece\u591a\u4e2a\u5217\u4e2d\u9009\u62e9\u7b2c\u4e00\u4e2a\u975e\u7a7a\u503c\u65f6\u7279\u522b\u6709\u7528：
\nSELECT COALESCE(your_column1, your_column2, '\u9ed8\u8ba4\u503c') FROM your_table;<\/p>\n
\u8fd9\u5c06\u8fd4\u56deyour_column1\u7684\u7b2c\u4e00\u4e2a\u975e\u7a7a\u503c，\u5982\u679c\u6ca1\u6709\u975e\u7a7a\u503c，\u5219\u8fd4\u56deyour_column2\u7684\u7b2c\u4e00\u4e2a\u975e\u7a7a\u503c，\u5982\u679c\u4e24\u8005\u90fd\u4e3a\u7a7a，\u5219\u8fd4\u56de'\u9ed8\u8ba4\u503c'\u3002
\n6. \u907f\u514d\u4f7f\u7528\u7b49\u53f7\u6bd4\u8f83NULL<\/p>\n
\u5c1d\u8bd5\u4f7f\u7528\u7b49\u53f7（=）\u6765\u6bd4\u8f83NULL\u4f1a\u5f97\u5230\u610f\u5916\u7684\u7ed3\u679c，\u56e0\u4e3a\u4efb\u4f55\u4e0eNULL\u7684\u6bd4\u8f83（\u5305\u62ec=）\u90fd\u4e0d\u4f1a\u8fd4\u56deTRUE<\/span>\u3002\u6b63\u786e\u7684\u505a\u6cd5\u662f\u4f7f\u7528IS NULL\u6216IS NOT NULL\u3002\u4f8b\u5982：
\n— \u9519\u8bef\u793a\u4f8b，\u4e0d\u4f1a\u6309\u9884\u671f\u5de5\u4f5c：
\nSELECT * FROM your_table WHERE your_column = NULL;\u00a0 — \u4e0d\u4f1a\u8fd4\u56de\u4efb\u4f55\u7ed3\u679c<\/p>\n7. \u4f7f\u7528JOIN\u5904\u7406NULL\u503c<\/p>\n
\u5728\u5904\u7406\u6d89\u53ca\u591a\u4e2a\u8868\u7684\u67e5\u8be2\u65f6，\u7279\u522b\u662f\u5728\u4f7f\u7528\u5916\u8fde\u63a5（LEFT JOIN, RIGHT JOIN）\u65f6，\u7406\u89e3\u5982\u4f55\u5904\u7406\u548c\u663e\u793aNULL\u503c\u975e\u5e38\u91cd\u8981\u3002\u4f8b\u5982：
\nSELECT a.*, b.some_column FROM table_a a
\nLEFT JOIN table_b b ON a.id = b.a_id;<\/p>\n
\u5728\u4e0a\u9762\u7684\u67e5\u8be2\u4e2d，\u5982\u679ctable_b\u4e2d\u6ca1\u6709\u5339\u914d\u7684\u884c，\u5219b.some_column\u5c06\u663e\u793a\u4e3aNULL\u3002
\n\u7ed3\u8bba<\/p>\n
\u7406\u89e3\u548c\u6b63\u786e\u5904\u7406Oracle\u4e2d\u7684NULL\u503c\u5bf9\u4e8e\u7f16\u5199\u6709\u6548\u548c\u53ef\u9760\u7684SQL\u67e5\u8be2\u81f3\u5173\u91cd\u8981\u3002\u4f7f\u7528\u9002\u5f53\u7684\u51fd\u6570\u548c\u6761\u4ef6（\u5982IS NULL, IS NOT NULL, NVL, COALESCE）\u53ef\u4ee5\u5e2e\u52a9\u6709\u6548\u5730\u7ba1\u7406\u548c\u67e5\u8be2\u8fd9\u4e9b\u503c\u3002<\/p><\/p>\n","protected":false},"excerpt":{"rendered":"
\u5728Oracle\u6570\u636e\u5e93\u4e2d，\u5904\u7406\u7a7a\u503c（NULL）\u548c\u67e5\u8be2\u7ed3\u679c\u65f6\u6709\u4e00\u4e9b\u91cd\u8981\u7684\u6982\u5ff5\u548c\u6280\u5de7\u3002
\n1. \u7406\u89e3NULL\u5728Oracle\u4e2d，NULL\u8868\u793a\u4e00\u4e2a\u7f3a\u5931\u7684\u6216\u672a\u77e5\u7684\u503c\u3002\u5b83\u4e0e\u4efb\u4f55\u5176\u4ed6\u503c（\u5305\u62ec0\u6216\u7a7a\u5b57\u7b26\u4e32）\u4e0d\u540c，\u56e0\u4e3a\u5b83\u4e0d\u662f\u4e00\u4e2a\u5177\u4f53\u7684\u503c\u3002\u4f8b\u5982，\u4e00\u4e2a\u5b57\u6bb5\u5982\u679c\u6ca1\u6709\u88ab\u660e\u786e\u8d4b\u503c，\u5b83\u5c06\u9ed8\u8ba4\u4e3aNULL\u3002
\n2. \u67e5\u8be2NULL\u503c\u8981\u67e5\u8be2NULL\u503c，\u53ef\u4ee5\u4f7f\u7528IS NULL\u6761\u4ef6\u3002\u4f8b<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[604,100],"topic":[],"class_list":["post-67121","post","type-post","status-publish","format-standard","hentry","category-server","tag-oracle","tag-100"],"yoast_head":"\n
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\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.wsisp.com\/helps\/67121.html","og_locale":"zh_CN","og_type":"article","og_title":"Oracle\uff1aNULL - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","og_description":"\u5728Oracle\u6570\u636e\u5e93\u4e2d，\u5904\u7406\u7a7a\u503c（NULL）\u548c\u67e5\u8be2\u7ed3\u679c\u65f6\u6709\u4e00\u4e9b\u91cd\u8981\u7684\u6982\u5ff5\u548c\u6280\u5de7\u3002 1. \u7406\u89e3NULL\u5728Oracle\u4e2d，NULL\u8868\u793a\u4e00\u4e2a\u7f3a\u5931\u7684\u6216\u672a\u77e5\u7684\u503c\u3002\u5b83\u4e0e\u4efb\u4f55\u5176\u4ed6\u503c（\u5305\u62ec0\u6216\u7a7a\u5b57\u7b26\u4e32）\u4e0d\u540c，\u56e0\u4e3a\u5b83\u4e0d\u662f\u4e00\u4e2a\u5177\u4f53\u7684\u503c\u3002\u4f8b\u5982，\u4e00\u4e2a\u5b57\u6bb5\u5982\u679c\u6ca1\u6709\u88ab\u660e\u786e\u8d4b\u503c，\u5b83\u5c06\u9ed8\u8ba4\u4e3aNULL\u3002 2. \u67e5\u8be2NULL\u503c\u8981\u67e5\u8be2NULL\u503c，\u53ef\u4ee5\u4f7f\u7528IS NULL\u6761\u4ef6\u3002\u4f8b","og_url":"https:\/\/www.wsisp.com\/helps\/67121.html","og_site_name":"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","article_published_time":"2026-01-28T02:25:23+00:00","author":"admin","twitter_card":"summary_large_image","twitter_misc":{"\u4f5c\u8005":"admin","\u9884\u8ba1\u9605\u8bfb\u65f6\u95f4":"1 \u5206"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/www.wsisp.com\/helps\/67121.html","url":"https:\/\/www.wsisp.com\/helps\/67121.html","name":"Oracle\uff1aNULL - 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