{"id":2616,"date":"2025-03-11T23:32:31","date_gmt":"2025-03-11T15:32:31","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=2616"},"modified":"2025-03-11T23:32:31","modified_gmt":"2025-03-11T15:32:31","slug":"postgresql-%e8%a1%a8%e8%be%be%e5%bc%8f%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/03\/11\/postgresql-%e8%a1%a8%e8%be%be%e5%bc%8f%e8%af%a6%e8%a7%a3\/","title":{"rendered":"PostgreSQL \u8868\u8fbe\u5f0f\u8be6\u89e3"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">\u5728 PostgreSQL \u4e2d\uff0c\u8868\u8fbe\u5f0f\uff08Expression\uff09\u662f\u7531\u4e00\u4e2a\u6216\u591a\u4e2a\u503c\u3001\u8fd0\u7b97\u7b26\u3001\u51fd\u6570\u548c SQL \u8bed\u53e5\u7ec4\u6210\u7684\u8ba1\u7b97\u5355\u5143\u3002\u8868\u8fbe\u5f0f\u7528\u4e8e\u67e5\u8be2\u3001\u66f4\u65b0\u3001\u63d2\u5165\u6570\u636e\u65f6\u7684\u8ba1\u7b97\u64cd\u4f5c\uff0c\u53ef\u4ee5\u8fd4\u56de\u5355\u4e2a\u503c\u6216\u4e00\u4e2a\u6570\u636e\u96c6\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>1. \u8868\u8fbe\u5f0f\u7684\u5206\u7c7b<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">PostgreSQL \u4e3b\u8981\u652f\u6301\u4ee5\u4e0b\u51e0\u7c7b\u8868\u8fbe\u5f0f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u7b97\u672f\u8868\u8fbe\u5f0f<\/strong><\/li>\n\n\n\n<li><strong>\u6bd4\u8f83\u8868\u8fbe\u5f0f<\/strong><\/li>\n\n\n\n<li><strong>\u903b\u8f91\u8868\u8fbe\u5f0f<\/strong><\/li>\n\n\n\n<li><strong>\u5b57\u7b26\u4e32\u8868\u8fbe\u5f0f<\/strong><\/li>\n\n\n\n<li><strong>\u65e5\u671f\u65f6\u95f4\u8868\u8fbe\u5f0f<\/strong><\/li>\n\n\n\n<li><strong>\u6570\u7ec4\u8868\u8fbe\u5f0f<\/strong><\/li>\n\n\n\n<li><strong>JSON \u8868\u8fbe\u5f0f<\/strong><\/li>\n\n\n\n<li><strong>CASE \u8868\u8fbe\u5f0f<\/strong><\/li>\n\n\n\n<li><strong>\u5b50\u67e5\u8be2\u8868\u8fbe\u5f0f<\/strong><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>2. \u7b97\u672f\u8868\u8fbe\u5f0f<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u7b97\u672f\u8868\u8fbe\u5f0f\u7528\u4e8e\u6267\u884c\u6570\u5b66\u8ba1\u7b97\uff0c\u6d89\u53ca <code>+<\/code>\u3001<code>-<\/code>\u3001<code>*<\/code>\u3001<code>\/<\/code>\u3001<code>%<\/code> \u7b49\u8fd0\u7b97\u7b26\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u793a\u4f8b<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT 10 + 5;  -- \u7ed3\u679c\uff1a15\nSELECT 20 - 4;  -- \u7ed3\u679c\uff1a16\nSELECT 8 * 7;   -- \u7ed3\u679c\uff1a56\nSELECT 10 \/ 2;  -- \u7ed3\u679c\uff1a5\nSELECT 10 % 3;  -- \u7ed3\u679c\uff1a1<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5e94\u7528\u5728\u67e5\u8be2\u8bed\u53e5\u4e2d\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT id, salary, salary * 1.1 AS new_salary FROM employees;<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4ee5\u4e0a\u67e5\u8be2\u4f1a\u8ba1\u7b97 <code>salary<\/code> \u589e\u957f 10% \u540e\u7684\u65b0\u503c\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>3. \u6bd4\u8f83\u8868\u8fbe\u5f0f<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u6bd4\u8f83\u8868\u8fbe\u5f0f\u7528\u4e8e\u6bd4\u8f83\u4e24\u4e2a\u503c\uff0c\u8fd4\u56de <code>TRUE<\/code> \u6216 <code>FALSE<\/code>\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u793a\u4f8b<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT 10 = 10;   -- \u7ed3\u679c\uff1aTRUE\nSELECT 10 &lt;&gt; 5;   -- \u7ed3\u679c\uff1aTRUE\nSELECT 10 &gt; 5;    -- \u7ed3\u679c\uff1aTRUE\nSELECT 10 &lt; 5;    -- \u7ed3\u679c\uff1aFALSE\nSELECT 10 &gt;= 10;  -- \u7ed3\u679c\uff1aTRUE\nSELECT 10 &lt;= 11;  -- \u7ed3\u679c\uff1aTRUE<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5e94\u7528\u5728 <code>WHERE<\/code> \u8bed\u53e5\u4e2d\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT * FROM employees WHERE salary &gt; 5000;<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>4. \u903b\u8f91\u8868\u8fbe\u5f0f<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u903b\u8f91\u8868\u8fbe\u5f0f\u7528\u4e8e\u7ec4\u5408\u591a\u4e2a\u6761\u4ef6\uff0c\u8fd4\u56de <code>TRUE<\/code> \u6216 <code>FALSE<\/code>\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u793a\u4f8b<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT TRUE AND FALSE;  -- \u7ed3\u679c\uff1aFALSE\nSELECT TRUE OR FALSE;   -- \u7ed3\u679c\uff1aTRUE\nSELECT NOT TRUE;        -- \u7ed3\u679c\uff1aFALSE<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u7528\u4e8e\u6570\u636e\u67e5\u8be2\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT * FROM employees WHERE age &gt; 30 AND department = 'IT';\nSELECT * FROM employees WHERE salary &gt; 7000 OR position = 'Manager';\nSELECT * FROM employees WHERE NOT department = 'HR';<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>5. \u5b57\u7b26\u4e32\u8868\u8fbe\u5f0f<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u5b57\u7b26\u4e32\u8868\u8fbe\u5f0f\u7528\u4e8e\u8fde\u63a5\u3001\u5339\u914d\u6216\u64cd\u4f5c\u5b57\u7b26\u4e32\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u793a\u4f8b<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT 'Hello' || ' World';  -- \u7ed3\u679c\uff1aHello World\nSELECT UPPER('postgresql');  -- \u7ed3\u679c\uff1aPOSTGRESQL\nSELECT LOWER('POSTGRESQL');  -- \u7ed3\u679c\uff1apostgresql\nSELECT LENGTH('database');   -- \u7ed3\u679c\uff1a8<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5e94\u7528\u5728\u67e5\u8be2\u4e2d\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT first_name || ' ' || last_name AS full_name FROM employees;<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>6. \u65e5\u671f\u65f6\u95f4\u8868\u8fbe\u5f0f<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u65e5\u671f\u65f6\u95f4\u8868\u8fbe\u5f0f\u7528\u4e8e\u64cd\u4f5c\u548c\u8ba1\u7b97\u65e5\u671f\u65f6\u95f4\u6570\u636e\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u793a\u4f8b<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT NOW();                 -- \u8fd4\u56de\u5f53\u524d\u65f6\u95f4\u6233\nSELECT CURRENT_DATE;          -- \u8fd4\u56de\u5f53\u524d\u65e5\u671f\nSELECT CURRENT_TIME;          -- \u8fd4\u56de\u5f53\u524d\u65f6\u95f4\nSELECT EXTRACT(YEAR FROM NOW()); -- \u63d0\u53d6\u5f53\u524d\u5e74\u4efd\nSELECT AGE('2000-01-01');     -- \u8ba1\u7b97\u4ece 2000 \u5e74 1 \u6708 1 \u65e5\u5230\u73b0\u5728\u7684\u65f6\u95f4\u5dee<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5e94\u7528\u5728\u67e5\u8be2\u4e2d\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT * FROM orders WHERE order_date &gt; CURRENT_DATE - INTERVAL '30 days';<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4ee5\u4e0a\u67e5\u8be2\u4f1a\u83b7\u53d6\u8fc7\u53bb 30 \u5929\u5185\u7684\u8ba2\u5355\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>7. \u6570\u7ec4\u8868\u8fbe\u5f0f<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u6570\u7ec4\u8868\u8fbe\u5f0f\u7528\u4e8e\u5b58\u50a8\u548c\u64cd\u4f5c\u6570\u7ec4\u6570\u636e\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u793a\u4f8b<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT ARRAY&#91;1, 2, 3] || ARRAY&#91;4, 5];  -- \u7ed3\u679c\uff1a{1,2,3,4,5}\nSELECT ARRAY&#91;10, 20, 30] @&gt; ARRAY&#91;20]; -- \u7ed3\u679c\uff1aTRUE\nSELECT ARRAY&#91;10, 20, 30] &lt;@ ARRAY&#91;10, 20, 30, 40]; -- \u7ed3\u679c\uff1aTRUE<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5e94\u7528\u5728\u67e5\u8be2\u4e2d\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT * FROM products WHERE tags @&gt; ARRAY&#91;'Electronics'];<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4ee5\u4e0a\u67e5\u8be2\u4f1a\u8fd4\u56de\u5305\u542b &#8220;Electronics&#8221; \u6807\u7b7e\u7684\u4ea7\u54c1\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>8. JSON \u8868\u8fbe\u5f0f<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">PostgreSQL \u652f\u6301 JSON \u6570\u636e\u7c7b\u578b\uff0c\u5e76\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684 JSON \u64cd\u4f5c\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u793a\u4f8b<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT '{\"name\": \"Alice\", \"age\": 25}'::jsonb -&gt; 'name';  -- \u7ed3\u679c\uff1a\"Alice\"\nSELECT '{\"person\": {\"name\": \"Bob\"}}'::jsonb #&gt; '{person, name}'; -- \u7ed3\u679c\uff1a\"Bob\"<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5e94\u7528\u5728\u67e5\u8be2\u4e2d\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT data-&gt;&gt;'name' FROM users WHERE data-&gt;&gt;'age' &gt; '30';<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4ee5\u4e0a\u67e5\u8be2\u4f1a\u83b7\u53d6\u5e74\u9f84\u5927\u4e8e 30 \u7684\u7528\u6237\u59d3\u540d\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>9. CASE \u8868\u8fbe\u5f0f<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>CASE<\/code> \u8868\u8fbe\u5f0f\u7528\u4e8e\u5b9e\u73b0\u6761\u4ef6\u5224\u65ad\uff0c\u76f8\u5f53\u4e8e SQL \u7248\u7684 <code>if-else<\/code>\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u793a\u4f8b<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT \n    first_name,\n    salary,\n    CASE \n        WHEN salary &gt; 10000 THEN 'High'\n        WHEN salary BETWEEN 5000 AND 10000 THEN 'Medium'\n        ELSE 'Low'\n    END AS salary_level\nFROM employees;<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>CASE<\/code> \u8868\u8fbe\u5f0f\u7684\u7528\u9014\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8ba1\u7b97\u5206\u7ea7<\/li>\n\n\n\n<li>\u6570\u636e\u8f6c\u6362<\/li>\n\n\n\n<li>\u52a8\u6001\u5206\u7ec4<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>10. \u5b50\u67e5\u8be2\u8868\u8fbe\u5f0f<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u5b50\u67e5\u8be2\u8868\u8fbe\u5f0f\u7528\u4e8e\u5d4c\u5957\u67e5\u8be2\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u793a\u4f8b<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT * FROM employees WHERE salary &gt; (SELECT AVG(salary) FROM employees);<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5e94\u7528\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT name FROM departments WHERE id IN (SELECT department_id FROM employees WHERE salary &gt; 7000);<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4ee5\u4e0a\u67e5\u8be2\u4f1a\u8fd4\u56de\u85aa\u8d44\u9ad8\u4e8e 7000 \u7684\u5458\u5de5\u6240\u5728\u7684\u90e8\u95e8\u540d\u79f0\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>\u603b\u7ed3<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">PostgreSQL \u63d0\u4f9b\u591a\u79cd\u7c7b\u578b\u7684\u8868\u8fbe\u5f0f\uff0c\u5e38\u89c1\u5305\u62ec\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u7b97\u672f\u8868\u8fbe\u5f0f<\/strong>\uff08\u6570\u5b66\u8ba1\u7b97\uff09<\/li>\n\n\n\n<li><strong>\u6bd4\u8f83\u8868\u8fbe\u5f0f<\/strong>\uff08\u503c\u6bd4\u8f83\uff09<\/li>\n\n\n\n<li><strong>\u903b\u8f91\u8868\u8fbe\u5f0f<\/strong>\uff08\u6761\u4ef6\u7ec4\u5408\uff09<\/li>\n\n\n\n<li><strong>\u5b57\u7b26\u4e32\u8868\u8fbe\u5f0f<\/strong>\uff08\u5b57\u7b26\u4e32\u5904\u7406\uff09<\/li>\n\n\n\n<li><strong>\u65e5\u671f\u65f6\u95f4\u8868\u8fbe\u5f0f<\/strong>\uff08\u65f6\u95f4\u8ba1\u7b97\uff09<\/li>\n\n\n\n<li><strong>\u6570\u7ec4\u8868\u8fbe\u5f0f<\/strong>\uff08\u6570\u7ec4\u64cd\u4f5c\uff09<\/li>\n\n\n\n<li><strong>JSON \u8868\u8fbe\u5f0f<\/strong>\uff08JSON \u5904\u7406\uff09<\/li>\n\n\n\n<li><strong>CASE \u8868\u8fbe\u5f0f<\/strong>\uff08\u6761\u4ef6\u5224\u65ad\uff09<\/li>\n\n\n\n<li><strong>\u5b50\u67e5\u8be2\u8868\u8fbe\u5f0f<\/strong>\uff08\u5d4c\u5957\u67e5\u8be2\uff09<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u638c\u63e1 PostgreSQL \u8868\u8fbe\u5f0f\uff0c\u53ef\u4ee5\u66f4\u7075\u6d3b\u5730\u6784\u9020 SQL \u8bed\u53e5\uff0c\u63d0\u9ad8\u6570\u636e\u67e5\u8be2\u548c\u64cd\u4f5c\u7684\u6548\u7387\uff01\u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5728 PostgreSQL \u4e2d\uff0c\u8868\u8fbe\u5f0f\uff08Expression\uff09\u662f\u7531\u4e00\u4e2a\u6216\u591a\u4e2a\u503c\u3001\u8fd0\u7b97\u7b26\u3001\u51fd\u6570\u548c SQL \u8bed\u53e5\u7ec4\u6210 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":2617,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[78],"tags":[],"class_list":["post-2616","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\/2616","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=2616"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2616\/revisions"}],"predecessor-version":[{"id":2618,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2616\/revisions\/2618"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/2617"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=2616"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=2616"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=2616"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}