{"id":2619,"date":"2025-03-11T23:34:11","date_gmt":"2025-03-11T15:34:11","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=2619"},"modified":"2025-03-11T23:34:11","modified_gmt":"2025-03-11T15:34:11","slug":"postgresql-where-%e5%ad%90%e5%8f%a5","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/03\/11\/postgresql-where-%e5%ad%90%e5%8f%a5\/","title":{"rendered":"PostgreSQL WHERE \u5b50\u53e5"},"content":{"rendered":"\n

WHERE<\/code> \u5b50\u53e5\u7528\u4e8e\u4ece\u6570\u636e\u5e93\u8868\u4e2d\u7b5b\u9009\u6570\u636e\uff0c\u4ec5\u8fd4\u56de\u6ee1\u8db3\u6307\u5b9a\u6761\u4ef6\u7684\u884c\u3002\u5b83\u901a\u5e38\u4e0e SELECT<\/code>\u3001UPDATE<\/code>\u3001DELETE<\/code> \u7b49 SQL \u8bed\u53e5\u4e00\u8d77\u4f7f\u7528\uff0c\u4ee5\u9650\u5236\u67e5\u8be2\u8303\u56f4\u3002<\/p>\n\n\n\n

\n\n\n\n

1. WHERE \u8bed\u6cd5<\/strong><\/h2>\n\n\n\n
SELECT column1, column2, ...\nFROM table_name\nWHERE condition;<\/code><\/pre>\n\n\n\n
    \n
  • condition<\/code> \u662f\u4e00\u4e2a\u8868\u8fbe\u5f0f\uff0c\u5b83\u8fd4\u56de TRUE<\/code>\u3001FALSE<\/code> \u6216 NULL<\/code>\u3002<\/li>\n\n\n\n
  • \u53ea\u6709 TRUE<\/code> \u7684\u884c\u4f1a\u88ab\u8fd4\u56de\u6216\u53d7\u5f71\u54cd\u3002<\/li>\n<\/ul>\n\n\n\n
    \n\n\n\n
    2. WHERE \u5b50\u53e5\u793a\u4f8b<\/strong><\/h2>\n\n\n\n
    \u5047\u8bbe\u6709\u4e00\u4e2a employees<\/code> \u8868\uff1a<\/p>\n\n\n\n
    CREATE TABLE employees (\n    id SERIAL PRIMARY KEY,\n    name VARCHAR(50),\n    age INT,\n    department VARCHAR(50),\n    salary DECIMAL(10,2)\n);\nINSERT INTO employees (name, age, department, salary) VALUES\n('Alice', 30, 'HR', 6000),\n('Bob', 35, 'IT', 8000),\n('Charlie', 28, 'Finance', 5500),\n('David', 40, 'IT', 9500),\n('Eve', 25, 'HR', 5000);<\/code><\/pre>\n\n\n\n
    2.1 \u4f7f\u7528 WHERE \u8fdb\u884c\u6761\u4ef6\u7b5b\u9009<\/strong><\/h3>\n\n\n\n
    SELECT * FROM employees WHERE age > 30;<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
    id | name  | age | department | salary\n---+-------+-----+-----------+--------\n2  | Bob   |  35 | IT        | 8000.00\n4  | David |  40 | IT        | 9500.00<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    3. WHERE \u5b50\u53e5\u4e2d\u7684\u5e38\u89c1\u8fd0\u7b97\u7b26<\/strong><\/h2>\n\n\n\n
    3.1 \u6bd4\u8f83\u8fd0\u7b97\u7b26<\/strong><\/h3>\n\n\n\n
    \u8fd0\u7b97\u7b26<\/th>\u8bf4\u660e<\/th><\/tr><\/thead>
    =<\/code><\/td>\u7b49\u4e8e<\/td><\/tr>
    <><\/code> \u6216 !=<\/code><\/td>\u4e0d\u7b49\u4e8e<\/td><\/tr>
    ><\/code><\/td>\u5927\u4e8e<\/td><\/tr>
    <<\/code><\/td>\u5c0f\u4e8e<\/td><\/tr>
    >=<\/code><\/td>\u5927\u4e8e\u7b49\u4e8e<\/td><\/tr>
    <=<\/code><\/td>\u5c0f\u4e8e\u7b49\u4e8e<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
    \u793a\u4f8b\uff1a<\/strong><\/p>\n\n\n\n
    SELECT * FROM employees WHERE salary >= 8000;<\/code><\/pre>\n\n\n\n
    id | name  | age | department | salary\n---+-------+-----+-----------+--------\n2  | Bob   |  35 | IT        | 8000.00\n4  | David |  40 | IT        | 9500.00<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    3.2 \u903b\u8f91\u8fd0\u7b97\u7b26<\/strong><\/h3>\n\n\n\n
    \u8fd0\u7b97\u7b26<\/th>\u8bf4\u660e<\/th><\/tr><\/thead>
    AND<\/code><\/td>\u903b\u8f91\u4e0e\uff08\u5fc5\u987b\u540c\u65f6\u6ee1\u8db3\u591a\u4e2a\u6761\u4ef6\uff09<\/td><\/tr>
    OR<\/code><\/td>\u903b\u8f91\u6216\uff08\u6ee1\u8db3\u4efb\u610f\u6761\u4ef6\u5373\u53ef\uff09<\/td><\/tr>
    NOT<\/code><\/td>\u903b\u8f91\u975e\uff08\u6392\u9664\u67d0\u4e9b\u6761\u4ef6\uff09<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
    \u793a\u4f8b\uff1a<\/strong><\/p>\n\n\n\n
    SELECT * FROM employees WHERE department = 'IT' AND salary > 8000;<\/code><\/pre>\n\n\n\n
    id | name  | age | department | salary\n---+-------+-----+-----------+--------\n4  | David |  40 | IT        | 9500.00<\/code><\/pre>\n\n\n\n
    SELECT * FROM employees WHERE department = 'HR' OR age < 30;<\/code><\/pre>\n\n\n\n
    id | name    | age | department | salary\n---+---------+-----+-----------+--------\n1  | Alice   | 30  | HR        | 6000.00\n3  | Charlie | 28  | Finance   | 5500.00\n5  | Eve     | 25  | HR        | 5000.00<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    3.3 BETWEEN\uff1a\u8303\u56f4\u67e5\u8be2<\/strong><\/h3>\n\n\n\n
    SELECT * FROM employees WHERE salary BETWEEN 5000 AND 8000;<\/code><\/pre>\n\n\n\n
    id | name    | age | department | salary\n---+---------+-----+-----------+--------\n1  | Alice   | 30  | HR        | 6000.00\n3  | Charlie | 28  | Finance   | 5500.00\n5  | Eve     | 25  | HR        | 5000.00<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    3.4 IN\uff1a\u591a\u9009\u5339\u914d<\/strong><\/h3>\n\n\n\n
    SELECT * FROM employees WHERE department IN ('HR', 'Finance');<\/code><\/pre>\n\n\n\n
    id | name    | age | department | salary\n---+---------+-----+-----------+--------\n1  | Alice   | 30  | HR        | 6000.00\n3  | Charlie | 28  | Finance   | 5500.00\n5  | Eve     | 25  | HR        | 5000.00<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    3.5 LIKE\uff1a\u6a21\u5f0f\u5339\u914d<\/strong><\/h3>\n\n\n\n
    \u901a\u914d\u7b26<\/th>\u8bf4\u660e<\/th><\/tr><\/thead>
    %<\/code><\/td>\u4ee3\u8868\u4efb\u610f\u6570\u91cf\u7684\u5b57\u7b26<\/td><\/tr>
    _<\/code><\/td>\u4ee3\u8868\u5355\u4e2a\u5b57\u7b26<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
    \u793a\u4f8b\uff1a\u67e5\u627e\u4ee5 A<\/code> \u5f00\u5934\u7684\u5458\u5de5<\/strong><\/p>\n\n\n\n
    SELECT * FROM employees WHERE name LIKE 'A%';<\/code><\/pre>\n\n\n\n
    id | name  | age | department | salary\n---+-------+-----+-----------+--------\n1  | Alice |  30 | HR        | 6000.00<\/code><\/pre>\n\n\n\n
    \u793a\u4f8b\uff1a\u67e5\u627e\u540d\u5b57\u957f\u5ea6\u4e3a 5 \u7684\u5458\u5de5<\/strong><\/p>\n\n\n\n
    SELECT * FROM employees WHERE name LIKE '_____';<\/code><\/pre>\n\n\n\n
    id | name  | age | department | salary\n---+-------+-----+-----------+--------\n2  | Bob   |  35 | IT        | 8000.00\n3  | David |  40 | IT        | 9500.00<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    3.6 IS NULL \/ IS NOT NULL<\/strong><\/h3>\n\n\n\n
    SELECT * FROM employees WHERE salary IS NULL;<\/code><\/pre>\n\n\n\n
    \u5982\u679c\u67d0\u4e2a\u5458\u5de5\u7684 salary<\/code> \u4e3a\u7a7a\uff0c\u8be5\u67e5\u8be2\u5c06\u8fd4\u56de\u7ed3\u679c\u3002<\/p>\n\n\n\n
    \n\n\n\n
    3.7 EXISTS \u5b50\u67e5\u8be2<\/strong><\/h3>\n\n\n\n
    \u67e5\u8be2 IT \u90e8\u95e8\u7684\u6240\u6709\u5458\u5de5<\/strong><\/p>\n\n\n\n
    SELECT * FROM employees e\nWHERE EXISTS (\n    SELECT 1 FROM employees WHERE department = 'IT' AND e.id = id\n);<\/code><\/pre>\n\n\n\n
    id | name  | age | department | salary\n---+-------+-----+-----------+--------\n2  | Bob   |  35 | IT        | 8000.00\n4  | David |  40 | IT        | 9500.00<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    4. WHERE \u5b50\u53e5\u5e94\u7528\u5728\u4e0d\u540c SQL \u8bed\u53e5<\/strong><\/h2>\n\n\n\n
    4.1 \u5728 UPDATE \u8bed\u53e5\u4e2d\u4f7f\u7528 WHERE<\/strong><\/h3>\n\n\n\n
    UPDATE employees SET salary = salary * 1.1 WHERE department = 'IT';<\/code><\/pre>\n\n\n\n
    \u5c06 IT \u90e8\u95e8\u7684\u5458\u5de5\u85aa\u8d44\u589e\u52a0 10%\u3002<\/p>\n\n\n\n
    \n\n\n\n
    4.2 \u5728 DELETE \u8bed\u53e5\u4e2d\u4f7f\u7528 WHERE<\/strong><\/h3>\n\n\n\n
    DELETE FROM employees WHERE age < 30;<\/code><\/pre>\n\n\n\n
    \u5220\u9664\u6240\u6709\u5c0f\u4e8e 30 \u5c81\u7684\u5458\u5de5\u3002<\/p>\n\n\n\n
    \n\n\n\n
    5. \u7ed3\u8bba<\/strong><\/h2>\n\n\n\n
      \n
    • WHERE<\/code> \u5b50\u53e5\u7528\u4e8e\u7b5b\u9009\u6570\u636e\uff0c\u4ec5\u8fd4\u56de\u6ee1\u8db3\u6761\u4ef6\u7684\u884c\u3002<\/li>\n\n\n\n
    • \u652f\u6301 \u6bd4\u8f83\u8fd0\u7b97\u7b26<\/strong> (=<\/code>, <><\/code>, ><\/code>, <<\/code>, BETWEEN<\/code>, IN<\/code>, LIKE<\/code> \u7b49)\u3002<\/li>\n\n\n\n
    • \u652f\u6301 \u903b\u8f91\u8fd0\u7b97\u7b26<\/strong> (AND<\/code>, OR<\/code>, NOT<\/code>) \u7ec4\u5408\u6761\u4ef6\u3002<\/li>\n\n\n\n
    • \u53ef\u7528\u4e8e SELECT<\/code>\u3001UPDATE<\/code>\u3001DELETE<\/code> \u7b49 SQL \u8bed\u53e5\u3002<\/li>\n<\/ul>\n\n\n\n
      \u901a\u8fc7 WHERE<\/code> \u5b50\u53e5\uff0c\u6211\u4eec\u53ef\u4ee5\u66f4\u7cbe\u51c6\u5730\u67e5\u8be2\u548c\u64cd\u4f5c\u6570\u636e\uff0c\u63d0\u9ad8\u6570\u636e\u5e93\u64cd\u4f5c\u7684\u6548\u7387\uff01\u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
      WHERE \u5b50\u53e5\u7528\u4e8e\u4ece\u6570\u636e\u5e93\u8868\u4e2d\u7b5b\u9009\u6570\u636e\uff0c\u4ec5\u8fd4\u56de\u6ee1\u8db3\u6307\u5b9a\u6761\u4ef6\u7684\u884c\u3002\u5b83\u901a\u5e38\u4e0e SELECT\u3001UPDATE\u3001DEL […]<\/p>\n","protected":false},"author":1,"featured_media":2620,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[78],"tags":[],"class_list":["post-2619","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-postgresql"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2619","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=2619"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2619\/revisions"}],"predecessor-version":[{"id":2621,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2619\/revisions\/2621"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/2620"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=2619"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=2619"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=2619"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}