{"id":1715,"date":"2025-02-16T08:42:48","date_gmt":"2025-02-16T00:42:48","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=1715"},"modified":"2025-02-16T08:42:48","modified_gmt":"2025-02-16T00:42:48","slug":"sql-first-%e5%87%bd%e6%95%b0","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/02\/16\/sql-first-%e5%87%bd%e6%95%b0\/","title":{"rendered":"SQL FIRST() \u51fd\u6570"},"content":{"rendered":"\n

FIRST()<\/code> \u51fd\u6570\u5728 SQL \u4e2d\u5e76\u4e0d\u662f\u6807\u51c6\u7684\u51fd\u6570\uff0c\u5b83\u5728\u67d0\u4e9b\u6570\u636e\u5e93\u7cfb\u7edf\uff08\u5982 MS Access\u3001MySQL\u3001SQLite \u7b49\uff09\u4e2d\u662f\u5b58\u5728\u7684\uff0c\u4f46\u5e76\u975e\u6240\u6709\u6570\u636e\u5e93\u90fd\u652f\u6301\u5b83\u3002\u8fd9\u4e2a\u51fd\u6570\u7684\u4f5c\u7528\u662f\u8fd4\u56de\u67d0\u4e2a\u5b57\u6bb5\u7684\u7b2c\u4e00\u6761\u8bb0\u5f55\uff08\u901a\u5e38\u6309\u67d0\u4e2a\u6392\u5e8f\u89c4\u5219\uff09\uff0c\u4e0d\u8fc7\u5b83\u7684\u5b9e\u73b0\u65b9\u5f0f\u548c\u652f\u6301\u60c5\u51b5\u6709\u6240\u4e0d\u540c\u3002<\/p>\n\n\n\n

1. FIRST()<\/code> \u51fd\u6570\u7b80\u4ecb<\/strong><\/h3>\n\n\n\n
    \n
  • \u4f5c\u7528<\/strong>\uff1a\u8fd4\u56de\u67d0\u4e2a\u5b57\u6bb5\u7684\u7b2c\u4e00\u6761\u8bb0\u5f55\uff08\u5373\u6309\u67d0\u4e2a\u6392\u5e8f\u89c4\u5219\u7684\u7b2c\u4e00\u4e2a\u503c\uff09\u3002<\/li>\n\n\n\n
  • \u5e38\u89c1\u7528\u9014<\/strong>\uff1a\u901a\u5e38\u7528\u4e8e\u9700\u8981\u9009\u51fa\u67d0\u4e2a\u8868\u4e2d\u67d0\u5217\u7684\u201c\u7b2c\u4e00\u6761\u201d\u6570\u636e\uff0c\u6216\u8005\u7528\u4e8e\u6309\u7279\u5b9a\u987a\u5e8f\u83b7\u53d6\u67d0\u4e2a\u5217\u7684\u7b2c\u4e00\u4e2a\u503c\u3002<\/li>\n<\/ul>\n\n\n\n

    2. \u652f\u6301\u7684\u6570\u636e\u5e93\u7cfb\u7edf<\/strong><\/h3>\n\n\n\n
      \n
    • \u652f\u6301\u7684\u6570\u636e\u5e93\u7cfb\u7edf<\/strong>\uff1aFIRST()<\/code> \u51fd\u6570\u5728\u4e00\u4e9b\u6570\u636e\u5e93\u4e2d\u662f\u53ef\u7528\u7684\uff0c\u6bd4\u5982 MS Access\u3001SQLite\u3001MySQL\uff08\u901a\u8fc7\u67d0\u4e9b\u7279\u5b9a\u65b9\u5f0f\u6a21\u62df\uff09\u3002<\/li>\n\n\n\n
    • \u4e0d\u652f\u6301\u7684\u6570\u636e\u5e93\u7cfb\u7edf<\/strong>\uff1a\u5728\u6807\u51c6 SQL\uff08\u5982 MySQL\u3001PostgreSQL\u3001SQL Server \u7b49\uff09\u4e2d\uff0c\u5e76\u4e0d\u76f4\u63a5\u652f\u6301 FIRST()<\/code> \u51fd\u6570\u3002\u5982\u679c\u4f60\u5728\u8fd9\u4e9b\u6570\u636e\u5e93\u4e2d\u9700\u8981\u7c7b\u4f3c\u7684\u529f\u80fd\uff0c\u901a\u5e38\u4f1a\u4f7f\u7528 LIMIT<\/code> \u6216 FETCH FIRST<\/code> \u7b49\u65b9\u6cd5\u3002<\/li>\n<\/ul>\n\n\n\n

      3. FIRST()<\/code> \u51fd\u6570\u7684\u57fa\u672c\u8bed\u6cd5\uff08MS Access \/ SQLite\uff09<\/strong><\/h3>\n\n\n\n
      SELECT FIRST(column_name)\nFROM table_name\nWHERE condition;<\/code><\/pre>\n\n\n\n
        \n
      • column_name<\/code>\uff1a\u8981\u8fd4\u56de\u7b2c\u4e00\u4e2a\u503c\u7684\u5217\u3002<\/li>\n\n\n\n
      • table_name<\/code>\uff1a\u8868\u7684\u540d\u79f0\u3002<\/li>\n\n\n\n
      • condition<\/code>\uff1a\u8fc7\u6ee4\u6761\u4ef6\uff08\u53ef\u9009\uff09\u3002<\/li>\n<\/ul>\n\n\n\n
        4. \u793a\u4f8b 1\uff1a\u8fd4\u56de\u7b2c\u4e00\u6761\u8bb0\u5f55<\/strong><\/h3>\n\n\n\n
        \u5047\u8bbe\u4f60\u6709\u4e00\u4e2a\u5458\u5de5\u8868 employees<\/code>\uff0c\u8868\u7ed3\u6784\u5982\u4e0b\uff1a<\/p>\n\n\n\n
        employee_id<\/th>name<\/th>salary<\/th><\/tr><\/thead>
        1<\/td>Tom<\/td>5000<\/td><\/tr>
        2<\/td>Jane<\/td>6000<\/td><\/tr>
        3<\/td>Bob<\/td>7000<\/td><\/tr>
        4<\/td>Alice<\/td>8000<\/td><\/tr>
        5<\/td>Mike<\/td>5500<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
        \u4f60\u5e0c\u671b\u83b7\u53d6\u5de5\u8d44\u5b57\u6bb5\u7684\u7b2c\u4e00\u4e2a\u503c\uff08\u6309\u9ed8\u8ba4\u6392\u5e8f\uff09\u3002\u5728\u652f\u6301 FIRST()<\/code> \u51fd\u6570\u7684\u6570\u636e\u5e93\u4e2d\uff0c\u67e5\u8be2\u8bed\u53e5\u5982\u4e0b\uff1a<\/p>\n\n\n\n
        SELECT FIRST(salary) AS first_salary\nFROM employees;<\/code><\/pre>\n\n\n\n
        \u8f93\u51fa\uff1a<\/strong><\/p>\n\n\n\n
        first_salary<\/th><\/tr><\/thead>
        5000<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
        \n
        \u6ce8\u610f\uff1a\u6b64\u67e5\u8be2\u8fd4\u56de\u7684\u662f\u8868\u4e2d salary<\/code> \u5217\u7684\u7b2c\u4e00\u4e2a\u8bb0\u5f55\uff0c\u6392\u5e8f\u89c4\u5219\u53d6\u51b3\u4e8e\u6570\u636e\u5e93\u7684\u9ed8\u8ba4\u6392\u5e8f\u65b9\u5f0f\uff08\u53ef\u80fd\u662f\u6309 employee_id<\/code> \u6216\u63d2\u5165\u987a\u5e8f\u7b49\uff09\u3002<\/p>\n<\/blockquote>\n\n\n\n
        5. \u5728 MySQL \u4e2d\u6a21\u62df FIRST()<\/code><\/strong><\/h3>\n\n\n\n
        MySQL \u5e76\u4e0d\u76f4\u63a5\u652f\u6301 FIRST()<\/code> \u51fd\u6570\uff0c\u4f46\u4f60\u53ef\u4ee5\u4f7f\u7528 ORDER BY<\/code> \u548c LIMIT<\/code> \u6765\u6a21\u62df\u7c7b\u4f3c\u7684\u529f\u80fd\u3002<\/p>\n\n\n\n
        \u4f8b\u5982\uff0c\u83b7\u53d6\u5458\u5de5\u8868\u4e2d\u7684\u6700\u4f4e\u5de5\u8d44\uff08\u6309\u5347\u5e8f\u6392\u5e8f\uff09\uff1a<\/p>\n\n\n\n
        SELECT salary\nFROM employees\nORDER BY salary ASC\nLIMIT 1;<\/code><\/pre>\n\n\n\n
        \u8f93\u51fa\uff1a<\/strong><\/p>\n\n\n\n
        salary<\/th><\/tr><\/thead>
        5000<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
        6. \u5728 SQL Server \u4e2d\u6a21\u62df FIRST()<\/code><\/strong><\/h3>\n\n\n\n
        SQL Server \u4e5f\u4e0d\u652f\u6301 FIRST()<\/code> \u51fd\u6570\uff0c\u4f46\u4f60\u53ef\u4ee5\u4f7f\u7528 TOP 1<\/code> \u548c ORDER BY<\/code> \u6765\u6a21\u62df\uff1a<\/p>\n\n\n\n
        SELECT TOP 1 salary\nFROM employees\nORDER BY salary ASC;<\/code><\/pre>\n\n\n\n
        7. \u5728 PostgreSQL \u4e2d\u6a21\u62df FIRST()<\/code><\/strong><\/h3>\n\n\n\n
        PostgreSQL \u540c\u6837\u4e0d\u652f\u6301 FIRST()<\/code> \u51fd\u6570\uff0c\u4f46\u53ef\u4ee5\u4f7f\u7528 LIMIT<\/code> \u6765\u6a21\u62df\uff1a<\/p>\n\n\n\n
        SELECT salary\nFROM employees\nORDER BY salary ASC\nLIMIT 1;<\/code><\/pre>\n\n\n\n
        8. FIRST()<\/code> \u51fd\u6570\u4e0e GROUP BY<\/code><\/strong><\/h3>\n\n\n\n
        \u5728\u67d0\u4e9b\u6570\u636e\u5e93\u4e2d\uff0cFIRST()<\/code> \u4e5f\u53ef\u4ee5\u4e0e GROUP BY<\/code> \u5b50\u53e5\u914d\u5408\u4f7f\u7528\uff0c\u8fd4\u56de\u6bcf\u4e2a\u5206\u7ec4\u7684\u7b2c\u4e00\u4e2a\u8bb0\u5f55\u3002<\/p>\n\n\n\n
        \u4f8b\u5982\uff0c\u5047\u8bbe\u4f60\u6709\u4e00\u4e2a orders<\/code> \u8868\uff0c\u8bb0\u5f55\u4e86\u6bcf\u4e2a\u5ba2\u6237\u7684\u8ba2\u5355\uff0c\u5e76\u4e14\u5e0c\u671b\u83b7\u5f97\u6bcf\u4e2a\u5ba2\u6237\u7684\u7b2c\u4e00\u4e2a\u8ba2\u5355\u91d1\u989d\uff08\u6309\u8ba2\u5355\u65f6\u95f4\u6392\u5e8f\uff09\uff1a<\/p>\n\n\n\n
        SELECT customer_id, FIRST(order_amount) AS first_order_amount\nFROM orders\nGROUP BY customer_id;<\/code><\/pre>\n\n\n\n
        \n
        \u6ce8\u610f<\/strong>\uff1a\u7531\u4e8e FIRST()<\/code> \u4e0d\u662f\u6807\u51c6 SQL \u51fd\u6570\uff0c\u53ef\u80fd\u4f1a\u9047\u5230\u4e0d\u540c\u7684\u6570\u636e\u5e93\u7cfb\u7edf\u652f\u6301\u6216\u4e0d\u652f\u6301\u7684\u60c5\u51b5\u3002\u5982\u679c\u4f7f\u7528\u7684\u662f\u4e0d\u652f\u6301 FIRST()<\/code> \u7684\u6570\u636e\u5e93\uff0c\u53ef\u4ee5\u901a\u8fc7 ORDER BY<\/code> \u548c LIMIT<\/code>\uff08\u6216 TOP<\/code>\uff09\u6765\u5b9e\u73b0\u76f8\u540c\u7684\u529f\u80fd\u3002<\/p>\n<\/blockquote>\n\n\n\n
        \u603b\u7ed3<\/h3>\n\n\n\n
          \n
        • FIRST()<\/code> \u51fd\u6570<\/strong>\uff1a\u662f\u4e00\u4e2a\u975e\u6807\u51c6\u7684 SQL \u805a\u5408\u51fd\u6570\uff0c\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u67d0\u4e2a\u5217\u7684\u7b2c\u4e00\u6761\u8bb0\u5f55\uff08\u901a\u5e38\u6309\u6392\u5e8f\u89c4\u5219\uff09\u3002<\/li>\n\n\n\n
        • \u652f\u6301\u7684\u6570\u636e\u5e93<\/strong>\uff1a\u5728 MS Access\u3001SQLite \u7b49\u6570\u636e\u5e93\u4e2d\uff0cFIRST()<\/code> \u53ef\u4ee5\u76f4\u63a5\u4f7f\u7528\u3002<\/li>\n\n\n\n
        • \u4e0d\u652f\u6301\u7684\u6570\u636e\u5e93<\/strong>\uff1a\u5728 MySQL\u3001PostgreSQL\u3001SQL Server \u7b49\u6570\u636e\u5e93\u4e2d\uff0cFIRST()<\/code> \u5e76\u4e0d\u76f4\u63a5\u652f\u6301\uff0c\u901a\u5e38\u53ef\u4ee5\u901a\u8fc7 LIMIT<\/code> \u6216 TOP<\/code> \u6765\u6a21\u62df\u3002<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"
          FIRST() \u51fd\u6570\u5728 SQL \u4e2d\u5e76\u4e0d\u662f\u6807\u51c6\u7684\u51fd\u6570\uff0c\u5b83\u5728\u67d0\u4e9b\u6570\u636e\u5e93\u7cfb\u7edf\uff08\u5982 MS Access\u3001MySQL\u3001S […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[36],"tags":[],"class_list":["post-1715","post","type-post","status-publish","format-standard","hentry","category-sql"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/1715","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/comments?post=1715"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/1715\/revisions"}],"predecessor-version":[{"id":1716,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/1715\/revisions\/1716"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=1715"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=1715"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=1715"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}