{"id":199,"date":"2026-07-09T09:57:25","date_gmt":"2026-07-09T01:57:25","guid":{"rendered":"https:\/\/yykcj.com\/?p=199"},"modified":"2026-07-09T09:57:25","modified_gmt":"2026-07-09T01:57:25","slug":"sql-%e6%80%a7%e8%83%bd%e8%b0%83%e4%bc%98%ef%bc%9a%e6%89%a7%e8%a1%8c%e8%ae%a1%e5%88%92%e5%88%86%e6%9e%90%e6%8c%87%e5%8d%97","status":"publish","type":"post","link":"https:\/\/yykcj.com\/?p=199","title":{"rendered":"SQL \u6027\u80fd\u8c03\u4f18\uff1a\u6267\u884c\u8ba1\u5212\u5206\u6790\u6307\u5357"},"content":{"rendered":"

\u4e3a\u4ec0\u4e48\u9700\u8981\u5206\u6790\u6267\u884c\u8ba1\u5212\uff1f<\/h2>\n

\u5728\u6570\u636e\u5e93\u5f00\u53d1\u4e2d\uff0c\u6211\u4eec\u7ecf\u5e38\u9047\u5230\u8fd9\u6837\u7684\u573a\u666f\uff1a\u4e00\u4e2a SQL \u67e5\u8be2\u5728\u6570\u636e\u91cf\u5c0f\u65f6\u8fd0\u884c\u98de\u5feb\uff0c\u4f46\u6570\u636e\u91cf\u589e\u957f\u540e\u53d8\u5f97\u5f02\u5e38\u7f13\u6162\u3002\u8fd9\u65f6\u5019\uff0c\u4ec5\u4ec5\u770b SQL \u8bed\u53e5\u672c\u8eab\u5f80\u5f80\u627e\u4e0d\u5230\u95ee\u9898\u6240\u5728\u3002\u6267\u884c\u8ba1\u5212\uff08Execution Plan\uff09\u662f\u6570\u636e\u5e93\u4f18\u5316\u5668\u6839\u636e SQL \u8bed\u53e5\u751f\u6210\u7684\u6267\u884c\u6b65\u9aa4\uff0c\u5b83\u63ed\u793a\u4e86\u6570\u636e\u5e93\u5982\u4f55\u8bbf\u95ee\u6570\u636e\u3001\u4f7f\u7528\u7d22\u5f15\u4ee5\u53ca\u8fde\u63a5\u8868\u7684\u65b9\u5f0f\u3002\u901a\u8fc7\u5206\u6790\u6267\u884c\u8ba1\u5212\uff0c\u6211\u4eec\u53ef\u4ee5\u7cbe\u51c6\u5b9a\u4f4d\u6027\u80fd\u74f6\u9888\uff0c\u4ece\u800c\u8fdb\u884c\u9488\u5bf9\u6027\u4f18\u5316\u3002<\/p>\n

\u672c\u6587\u5c06\u4f7f\u7528 PostgreSQL \u6570\u636e\u5e93\u4e3a\u4f8b\uff0c\u4f46\u539f\u7406\u540c\u6837\u9002\u7528\u4e8e MySQL\u3001Oracle \u7b49\u5176\u4ed6\u6570\u636e\u5e93\u3002<\/p>\n

\u83b7\u53d6\u6267\u884c\u8ba1\u5212<\/h2>\n

\u4f7f\u7528 EXPLAIN<\/h3>\n

PostgreSQL \u4e2d\uff0c\u4f7f\u7528 EXPLAIN<\/code> \u547d\u4ee4\u53ef\u4ee5\u67e5\u770b\u6267\u884c\u8ba1\u5212\uff1a<\/p>\n

\nEXPLAIN SELECT * FROM users WHERE age > 30;\n<\/code><\/pre>\n
\u8f93\u51fa\u793a\u4f8b\uff1a<\/p>\n
\nSeq Scan on users  (cost=0.00..35.00 rows=10 width=100)\n  Filter: (age > 30)\n<\/code><\/pre>\n
\u4f7f\u7528 EXPLAIN ANALYZE<\/h3>\n
EXPLAIN ANALYZE<\/code> \u4f1a\u5b9e\u9645\u6267\u884c SQL\uff0c\u5e76\u8fd4\u56de\u771f\u5b9e\u7684\u6267\u884c\u65f6\u95f4\u548c\u884c\u6570\uff0c\u66f4\u51c6\u786e\uff1a<\/p>\n
\nEXPLAIN ANALYZE SELECT * FROM users WHERE age > 30;\n<\/code><\/pre>\n
\u8f93\u51fa\u793a\u4f8b\uff1a<\/p>\n
\nSeq Scan on users  (cost=0.00..35.00 rows=10 width=100) (actual time=0.015..0.020 rows=5 loops=1)\n  Filter: (age > 30)\n  Rows Removed by Filter: 995\n<\/code><\/pre>\n
\ud83d\udca1 \u6ce8\u610f<\/strong>\uff1aEXPLAIN ANALYZE<\/code> \u4f1a\u5b9e\u9645\u4fee\u6539\u6570\u636e\uff08\u5982 INSERT\/UPDATE\/DELETE\uff09\uff0c\u5efa\u8bae\u5728\u4e8b\u52a1\u4e2d\u6267\u884c\u5e76\u56de\u6eda\u3002<\/p>\n
\u89e3\u8bfb\u6267\u884c\u8ba1\u5212\u7684\u5173\u952e\u6307\u6807<\/h2>\n
1. \u8282\u70b9\u7c7b\u578b<\/h3>\n
    \n
  • Seq Scan<\/strong>\uff1a\u5168\u8868\u626b\u63cf\uff0c\u901a\u5e38\u6548\u7387\u4f4e\uff0c\u5e94\u907f\u514d\u3002<\/li>\n
  • Index Scan<\/strong>\uff1a\u7d22\u5f15\u626b\u63cf\uff0c\u5feb\u901f\u5b9a\u4f4d\u6570\u636e\u3002<\/li>\n
  • Index Only Scan<\/strong>\uff1a\u4ec5\u7d22\u5f15\u626b\u63cf\uff0c\u65e0\u9700\u56de\u8868\uff0c\u66f4\u5feb\u3002<\/li>\n
  • Nested Loop<\/strong>\uff1a\u5d4c\u5957\u5faa\u73af\u8fde\u63a5\uff0c\u9002\u5408\u5c0f\u8868\u9a71\u52a8\u5927\u8868\u3002<\/li>\n
  • Hash Join<\/strong>\uff1a\u54c8\u5e0c\u8fde\u63a5\uff0c\u9002\u5408\u5927\u8868\u7b49\u503c\u8fde\u63a5\u3002<\/li>\n
  • Merge Join<\/strong>\uff1a\u5f52\u5e76\u8fde\u63a5\uff0c\u9002\u5408\u6392\u5e8f\u540e\u7684\u6570\u636e\u3002<\/li>\n<\/ul>\n
    2. \u6210\u672c\u4f30\u7b97<\/h3>\n
    cost=0.00..35.00<\/code> \u8868\u793a\u542f\u52a8\u6210\u672c\u5230\u603b\u6210\u672c\u3002\u5355\u4f4d\u662f\u4efb\u610f\u5355\u4f4d\uff0c\u4f46\u76f8\u5bf9\u5927\u5c0f\u6709\u610f\u4e49\u3002<\/p>\n
      \n
    • \u542f\u52a8\u6210\u672c\uff1a\u8fd4\u56de\u7b2c\u4e00\u884c\u524d\u7684\u6210\u672c\u3002<\/li>\n
    • \u603b\u6210\u672c\uff1a\u8fd4\u56de\u6240\u6709\u884c\u7684\u6210\u672c\u3002<\/li>\n<\/ul>\n
      3. \u5b9e\u9645\u65f6\u95f4\u4e0e\u884c\u6570<\/h3>\n
      actual time=0.015..0.020 rows=5 loops=1<\/code> \u8868\u793a\u5b9e\u9645\u6267\u884c\u65f6\u95f4\uff08\u6beb\u79d2\uff09\u548c\u8fd4\u56de\u884c\u6570\u3002\u5982\u679c\u4e0e\u4f30\u7b97\u76f8\u5dee\u5f88\u5927\uff0c\u8bf4\u660e\u7edf\u8ba1\u4fe1\u606f\u53ef\u80fd\u8fc7\u65f6\u3002<\/p>\n
      4. \u7f13\u51b2\u533a\u4fe1\u606f<\/h3>\n
      \u4f7f\u7528 BUFFERS<\/code> \u9009\u9879\u53ef\u4ee5\u67e5\u770b\u7f13\u5b58\u547d\u4e2d\u60c5\u51b5\uff1a<\/p>\n
      \nEXPLAIN (ANALYZE, BUFFERS) SELECT * FROM users WHERE age > 30;\n<\/code><\/pre>\n
      \u8f93\u51fa\u793a\u4f8b\uff1a<\/p>\n
      \nSeq Scan on users  (cost=0.00..35.00 rows=10 width=100) (actual time=0.015..0.020 rows=5 loops=1)\n  Buffers: shared hit=100 read=0\n<\/code><\/pre>\n
        \n
      • shared hit<\/code>\uff1a\u4ece\u7f13\u5b58\u8bfb\u53d6\u7684\u5757\u6570\u3002<\/li>\n
      • shared read<\/code>\uff1a\u4ece\u78c1\u76d8\u8bfb\u53d6\u7684\u5757\u6570\u3002<\/li>\n<\/ul>\n
        \u5b9e\u6218\u8c03\u4f18\u6848\u4f8b<\/h2>\n
        \u6848\u4f8b1\uff1a\u5168\u8868\u626b\u63cf\u4f18\u5316<\/h3>\n
        \u6162\u67e5\u8be2<\/strong>\uff1a<\/p>\n
        \nSELECT * FROM orders WHERE order_date >= '2023-01-01';\n<\/code><\/pre>\n
        \u6267\u884c\u8ba1\u5212\uff1a<\/p>\n
        \nSeq Scan on orders  (cost=0.00..5000.00 rows=1000 width=200) (actual time=0.100..50.000 rows=5000 loops=1)\n  Filter: (order_date >= '2023-01-01'::date)\n<\/code><\/pre>\n
        \u95ee\u9898<\/strong>\uff1a\u5168\u8868\u626b\u63cf\uff0c\u6570\u636e\u91cf\u5927\u65f6\u6162\u3002<\/p>\n
        \u4f18\u5316<\/strong>\uff1a\u521b\u5efa\u7d22\u5f15<\/p>\n
        \nCREATE INDEX idx_order_date ON orders(order_date);\n<\/code><\/pre>\n
        \u518d\u6b21\u6267\u884c\u8ba1\u5212\uff1a<\/p>\n
        \nIndex Scan using idx_order_date on orders  (cost=0.29..150.00 rows=1000 width=200) (actual time=0.020..5.000 rows=5000 loops=1)\n  Index Cond: (order_date >= '2023-01-01'::date)\n<\/code><\/pre>\n
        \u6210\u672c\u4ece 5000 \u964d\u5230 150\uff0c\u65f6\u95f4\u4ece 50ms \u964d\u5230 5ms\u3002<\/p>\n
        \u6848\u4f8b2\uff1a\u8fde\u63a5\u67e5\u8be2\u4f18\u5316<\/h3>\n
        \u6162\u67e5\u8be2<\/strong>\uff1a<\/p>\n
        \nSELECT * FROM users u JOIN orders o ON u.id = o.user_id WHERE u.age > 30;\n<\/code><\/pre>\n
        \u6267\u884c\u8ba1\u5212\uff1a<\/p>\n
        \nHash Join  (cost=100.00..5000.00 rows=1000 width=300) (actual time=10.000..100.000 rows=5000 loops=1)\n  Hash Cond: (o.user_id = u.id)\n  -> Seq Scan on orders o  (cost=0.00..4000.00 rows=100000 width=200) (actual time=0.100..80.000 rows=100000 loops=1)\n  -> Hash  (cost=50.00..50.00 rows=1000 width=100) (actual time=0.500..0.500 rows=1000 loops=1)\n        Buckets: 1024  Batches: 1  Memory Usage: 40kB\n        -> Seq Scan on users u  (cost=0.00..50.00 rows=1000 width=100) (actual time=0.010..0.200 rows=1000 loops=1)\n              Filter: (age > 30)\n<\/code><\/pre>\n
        \u95ee\u9898<\/strong>\uff1aorders \u8868\u5168\u8868\u626b\u63cf\uff0c\u4e14 Hash Join \u6784\u5efa\u54c8\u5e0c\u8868\u6d88\u8017\u5185\u5b58\u3002<\/p>\n
        \u4f18\u5316<\/strong>\uff1a<\/p>\n
          \n
        1. \u4e3a orders.user_id \u521b\u5efa\u7d22\u5f15\uff1a<\/li>\n<\/ol>\n
          \nCREATE INDEX idx_orders_user_id ON orders(user_id);\n<\/code><\/pre>\n
            \n
          1. \u4e3a users.age \u521b\u5efa\u7d22\u5f15\uff08\u5df2\u5b58\u5728\uff09\u3002<\/li>\n<\/ol>\n
            \u4f18\u5316\u540e\u6267\u884c\u8ba1\u5212\uff1a<\/p>\n
            \nNested Loop  (cost=0.29..2000.00 rows=1000 width=300) (actual time=0.010..20.000 rows=5000 loops=1)\n  -> Index Scan using idx_users_age on users u  (cost=0.29..50.00 rows=1000 width=100) (actual time=0.010..5.000 rows=1000 loops=1)\n        Index Cond: (age > 30)\n  -> Index Scan using idx_orders_user_id on orders o  (cost=0.00..1.50 rows=10 width=200) (actual time=0.010..0.015 rows=5 loops=1000)\n        Index Cond: (user_id = u.id)\n<\/code><\/pre>\n
            \u6210\u672c\u4ece 5000 \u964d\u5230 2000\uff0c\u65f6\u95f4\u4ece 100ms \u964d\u5230 20ms\u3002<\/p>\n
            \u6848\u4f8b3\uff1a\u6392\u5e8f\u4f18\u5316<\/h3>\n
            \u6162\u67e5\u8be2<\/strong>\uff1a<\/p>\n
            \nSELECT * FROM products ORDER BY price DESC LIMIT 10;\n<\/code><\/pre>\n
            \u6267\u884c\u8ba1\u5212\uff1a<\/p>\n
            \nLimit  (cost=5000.00..5000.10 rows=10 width=100) (actual time=100.000..100.010 rows=10 loops=1)\n  -> Sort  (cost=5000.00..6000.00 rows=100000 width=100) (actual time=100.000..100.005 rows=10 loops=1)\n        Sort Key: price DESC\n        Sort Method: external merge  Disk: 2048kB\n        -> Seq Scan on products  (cost=0.00..4000.00 rows=100000 width=100) (actual time=0.100..80.000 rows=100000 loops=1)\n<\/code><\/pre>\n
            \u95ee\u9898<\/strong>\uff1a\u5168\u8868\u626b\u63cf\u540e\u6392\u5e8f\uff0c\u4f7f\u7528\u4e86\u78c1\u76d8\u6392\u5e8f\uff08external merge\uff09\uff0c\u975e\u5e38\u6162\u3002<\/p>\n
            \u4f18\u5316<\/strong>\uff1a\u521b\u5efa\u7d22\u5f15<\/p>\n
            \nCREATE INDEX idx_products_price ON products(price DESC);\n<\/code><\/pre>\n
            \u4f18\u5316\u540e\uff1a<\/p>\n
            \nLimit  (cost=0.29..1.00 rows=10 width=100) (actual time=0.010..0.020 rows=10 loops=1)\n  -> Index Scan Backward using idx_products_price on products  (cost=0.29..7000.00 rows=100000 width=100) (actual time=0.010..0.015 rows=10 loops=1)\n<\/code><\/pre>\n
            \u6210\u672c\u4ece 5000 \u964d\u5230 1\uff0c\u65f6\u95f4\u4ece 100ms \u964d\u5230 0.02ms\u3002<\/p>\n
            \u5e38\u89c1\u9677\u9631\u4e0e\u6700\u4f73\u5b9e\u8df5<\/h2>\n
            1. \u7edf\u8ba1\u4fe1\u606f\u8fc7\u65f6<\/h3>\n
            \u5982\u679c\u6267\u884c\u8ba1\u5212\u4e2d\u4f30\u7b97\u884c\u6570\u4e0e\u5b9e\u9645\u884c\u6570\u5dee\u5f02\u5f88\u5927\uff0c\u53ef\u80fd\u662f\u7edf\u8ba1\u4fe1\u606f\u672a\u66f4\u65b0\uff1a<\/p>\n
            \nANALYZE table_name;\n<\/code><\/pre>\n
            2. \u7d22\u5f15\u672a\u88ab\u4f7f\u7528<\/h3>\n
            \u53ef\u80fd\u539f\u56e0\uff1a<\/p>\n
              \n
            • \u67e5\u8be2\u6761\u4ef6\u4f7f\u7528\u4e86\u51fd\u6570\u6216\u7c7b\u578b\u8f6c\u6362\uff08\u5982 WHERE DATE(column) = '2023-01-01'<\/code> \u5e94\u6539\u4e3a WHERE column >= '2023-01-01' AND column < '2023-01-02'<\/code>\uff09<\/li>\n
            • \u4f7f\u7528\u4e86 LIKE '%keyword'<\/code> \u65e0\u6cd5\u4f7f\u7528\u7d22\u5f15<\/li>\n
            • \u6570\u636e\u5206\u5e03\u5bfc\u81f4\u4f18\u5316\u5668\u8ba4\u4e3a\u5168\u8868\u626b\u63cf\u66f4\u4f18\uff08\u5982\u5927\u90e8\u5206\u6570\u636e\u6ee1\u8db3\u6761\u4ef6\uff09<\/li>\n<\/ul>\n
              3. \u5d4c\u5957\u5faa\u73af vs \u54c8\u5e0c\u8fde\u63a5<\/h3>\n
                \n
              • \u5f53\u9a71\u52a8\u8868\u5c0f\u4e14\u5185\u8868\u6709\u7d22\u5f15\u65f6\uff0c\u5d4c\u5957\u5faa\u73af\u5feb\u3002<\/li>\n
              • \u5f53\u4e24\u8868\u90fd\u5927\u4e14\u65e0\u7d22\u5f15\u65f6\uff0c\u54c8\u5e0c\u8fde\u63a5\u66f4\u4f18\u3002<\/li>\n<\/ul>\n
                \u53ef\u4ee5\u901a\u8fc7 SET enable_nestloop = off;<\/code> \u4e34\u65f6\u7981\u7528\u67d0\u79cd\u8fde\u63a5\u65b9\u5f0f\u6d4b\u8bd5\u3002<\/p>\n
                4. \u4f7f\u7528 pgstat<\/em>statements \u76d1\u63a7<\/h3>\n
                \u5b89\u88c5\u6269\u5c55\u540e\uff0c\u53ef\u4ee5\u67e5\u770b\u9ad8\u9891\u6162\u67e5\u8be2\uff1a<\/p>\n
                \nCREATE EXTENSION pg_stat_statements;\nSELECT query, calls, total_time, mean_time FROM pg_stat_statements ORDER BY total_time DESC LIMIT 10;\n<\/code><\/pre>\n
                \u603b\u7ed3<\/h2>\n
                \u901a\u8fc7\u6267\u884c\u8ba1\u5212\u5206\u6790\uff0c\u6211\u4eec\u53ef\u4ee5\uff1a<\/p>\n
                  \n
                1. \u8bc6\u522b\u5168\u8868\u626b\u63cf\u3001\u6392\u5e8f\u7b49\u4f4e\u6548\u64cd\u4f5c\u3002<\/li>\n
                2. \u9a8c\u8bc1\u7d22\u5f15\u662f\u5426\u88ab\u6709\u6548\u4f7f\u7528\u3002<\/li>\n
                3. \u53d1\u73b0\u7edf\u8ba1\u4fe1\u606f\u95ee\u9898\u3002<\/li>\n
                4. \u5bf9\u6bd4\u4e0d\u540c\u67e5\u8be2\u5199\u6cd5\u6216\u7d22\u5f15\u65b9\u6848\u7684\u6548\u679c\u3002<\/li>\n<\/ol>\n
                  \u5efa\u8bae\u5728\u65e5\u5e38\u5f00\u53d1\u4e2d\uff0c\u5bf9\u6bcf\u4e2a\u53ef\u80fd\u4ea7\u751f\u6027\u80fd\u95ee\u9898\u7684 SQL \u90fd\u6267\u884c EXPLAIN ANALYZE<\/code>\uff0c\u786e\u4fdd\u5176\u6267\u884c\u8ba1\u5212\u5408\u7406\u3002<\/p>\n
                  \u5ef6\u4f38\u9605\u8bfb<\/strong>\uff1a<\/p>\n
                    \n
                  • PostgreSQL \u5b98\u65b9\u6587\u6863\uff1aEXPLAIN<\/li>\n
                  • \u7d22\u5f15\u7c7b\u578b\uff1aB-tree\u3001Hash\u3001GiST\u3001GIN \u7b49\u9002\u7528\u573a\u666f<\/li>\n
                  • \u67e5\u8be2\u91cd\u5199\u6280\u5de7\uff1a\u5b50\u67e5\u8be2 vs JOIN\uff0c\u4f7f\u7528 WITH \u7b49<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"
                    \u672c\u6587\u6df1\u5165\u8bb2\u89e3\u5982\u4f55\u901a\u8fc7\u5206\u6790 SQL \u6267\u884c\u8ba1\u5212\u6765\u4f18\u5316\u67e5\u8be2\u6027\u80fd\u3002\u4ece\u83b7\u53d6\u6267\u884c\u8ba1\u5212\u3001\u89e3\u8bfb\u5173\u952e\u6307\u6807\u5230\u5b9e\u9645\u8c03\u4f18\u6848\u4f8b\uff0c\u624b\u628a\u624b\u5e26\u4f60\u638c\u63e1\u6027\u80fd\u8c03\u4f18\u7684\u6838\u5fc3\u6280\u80fd\u3002<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,4],"tags":[114,111,112,113,115],"class_list":["post-199","post","type-post","status-publish","format-standard","hentry","category-3","category-4","tag-postgresql","tag-sql","tag-112","tag-113","tag-115"],"_links":{"self":[{"href":"https:\/\/yykcj.com\/index.php?rest_route=\/wp\/v2\/posts\/199","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/yykcj.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/yykcj.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/yykcj.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/yykcj.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=199"}],"version-history":[{"count":0,"href":"https:\/\/yykcj.com\/index.php?rest_route=\/wp\/v2\/posts\/199\/revisions"}],"wp:attachment":[{"href":"https:\/\/yykcj.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=199"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/yykcj.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=199"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/yykcj.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=199"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}