{"id":2663,"date":"2025-03-12T23:36:28","date_gmt":"2025-03-12T15:36:28","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=2663"},"modified":"2025-03-12T23:36:28","modified_gmt":"2025-03-12T15:36:28","slug":"postgresql-%e5%88%ab%e5%90%8d%ef%bc%88alias%ef%bc%89%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/03\/12\/postgresql-%e5%88%ab%e5%90%8d%ef%bc%88alias%ef%bc%89%e8%af%a6%e8%a7%a3\/","title":{"rendered":"PostgreSQL \u522b\u540d\uff08Alias\uff09\u8be6\u89e3"},"content":{"rendered":"\n

\u5728 PostgreSQL \u4e2d\uff0c\u522b\u540d\uff08Alias\uff09<\/strong> \u4e3b\u8981\u7528\u4e8e\u7ed9 \u8868\uff08Table\uff09<\/strong> \u6216 \u5217\uff08Column\uff09<\/strong> \u8d4b\u4e88\u4e34\u65f6\u540d\u79f0\uff0c\u4f7f SQL \u8bed\u53e5\u66f4\u52a0\u7b80\u6d01\u6613\u8bfb\u3002\u522b\u540d\u53ea\u5728\u67e5\u8be2\u8bed\u53e5\u6267\u884c\u65f6\u6709\u6548\uff0c\u4e0d\u4f1a\u5f71\u54cd\u6570\u636e\u5e93\u7684\u5b9e\u9645\u7ed3\u6784\u3002<\/p>\n\n\n\n

\n\n\n\n

1. \u5217\u522b\u540d\uff08Column Alias\uff09<\/strong><\/h2>\n\n\n\n

\u8bed\u6cd5<\/strong>\uff1a<\/p>\n\n\n\n

SELECT column_name AS alias_name FROM table_name;<\/code><\/pre>\n\n\n\n
\u6216\uff08AS<\/code> \u5173\u952e\u5b57\u53ef\u4ee5\u7701\u7565\uff09\uff1a<\/p>\n\n\n\n
SELECT column_name alias_name FROM table_name;<\/code><\/pre>\n\n\n\n
\u793a\u4f8b<\/strong>\uff1a
\u5047\u8bbe\u6709\u4e00\u4e2a employees<\/code> \u8868\uff1a<\/p>\n\n\n\n
CREATE TABLE employees (\n    emp_id SERIAL PRIMARY KEY,\n    first_name VARCHAR(50),\n    last_name VARCHAR(50),\n    salary DECIMAL(10, 2)\n);\nINSERT INTO employees (first_name, last_name, salary) VALUES\n('Alice', 'Smith', 5000),\n('Bob', 'Johnson', 6000),\n('Charlie', 'Brown', 7000);<\/code><\/pre>\n\n\n\n
\u4f7f\u7528\u5217\u522b\u540d<\/strong>\uff1a<\/p>\n\n\n\n
SELECT first_name AS \"First Name\", last_name AS \"Last Name\", salary * 12 AS \"Annual Salary\"\nFROM employees;<\/code><\/pre>\n\n\n\n
\u7ed3\u679c<\/strong>\uff1a<\/p>\n\n\n\n
First Name<\/th>Last Name<\/th>Annual Salary<\/th><\/tr><\/thead>
Alice<\/td>Smith<\/td>60000<\/td><\/tr>
Bob<\/td>Johnson<\/td>72000<\/td><\/tr>
Charlie<\/td>Brown<\/td>84000<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\u6ce8\u610f<\/strong>\uff1a<\/p>\n\n\n\n
    \n
  • \u5982\u679c\u522b\u540d\u5305\u542b \u7a7a\u683c\u6216\u7279\u6b8a\u5b57\u7b26<\/strong>\uff0c\u5fc5\u987b\u7528 \u53cc\u5f15\u53f7<\/code> \"\"<\/code> \u5305\u88f9\u3002<\/li>\n\n\n\n
  • AS<\/code> \u5173\u952e\u5b57\u53ef\u4ee5\u7701\u7565\uff0c\u4f46\u5efa\u8bae\u4f7f\u7528\uff0c\u63d0\u9ad8\u53ef\u8bfb\u6027\u3002<\/li>\n<\/ul>\n\n\n\n
    \n\n\n\n
    2. \u8868\u522b\u540d\uff08Table Alias\uff09<\/strong><\/h2>\n\n\n\n
    \u8bed\u6cd5<\/strong>\uff1a<\/p>\n\n\n\n
    SELECT column_name FROM table_name AS alias_name;<\/code><\/pre>\n\n\n\n
    \u6216\uff1a<\/p>\n\n\n\n
    SELECT column_name FROM table_name alias_name;<\/code><\/pre>\n\n\n\n
    \u793a\u4f8b<\/strong>\uff1a<\/p>\n\n\n\n
    SELECT e.first_name, e.last_name, e.salary\nFROM employees AS e;<\/code><\/pre>\n\n\n\n
    \u6216\u7701\u7565 AS<\/code>\uff1a<\/p>\n\n\n\n
    SELECT e.first_name, e.last_name, e.salary\nFROM employees e;<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c<\/strong>\uff1a<\/p>\n\n\n\n
    first_name<\/th>last_name<\/th>salary<\/th><\/tr><\/thead>
    Alice<\/td>Smith<\/td>5000<\/td><\/tr>
    Bob<\/td>Johnson<\/td>6000<\/td><\/tr>
    Charlie<\/td>Brown<\/td>7000<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
    \u4e3a\u4ec0\u4e48\u4f7f\u7528\u8868\u522b\u540d\uff1f<\/strong><\/p>\n\n\n\n
      \n
    • \u9002\u7528\u4e8e \u591a\u8868 JOIN<\/strong> \u65f6\uff0c\u7b80\u5316\u8868\u540d\uff0c\u63d0\u9ad8 SQL \u8bed\u53e5\u7684\u53ef\u8bfb\u6027\u3002<\/li>\n\n\n\n
    • \u907f\u514d\u8868\u540d\u8fc7\u957f\u5bfc\u81f4\u7684\u5197\u4f59\u3002<\/li>\n<\/ul>\n\n\n\n
      \n\n\n\n
      3. \u5728 JOIN \u8bed\u53e5\u4e2d\u4f7f\u7528\u8868\u522b\u540d<\/strong><\/h2>\n\n\n\n
      \u5982\u679c\u6ca1\u6709\u522b\u540d\uff0c\u6bcf\u6b21\u90fd\u8981\u5199\u5b8c\u6574\u8868\u540d\uff1a<\/p>\n\n\n\n
      SELECT employees.first_name, employees.last_name, departments.department_name\nFROM employees\nJOIN departments ON employees.emp_id = departments.emp_id;<\/code><\/pre>\n\n\n\n
      \u4f7f\u7528\u8868\u522b\u540d\u4f18\u5316<\/strong>\uff1a<\/p>\n\n\n\n
      SELECT e.first_name, e.last_name, d.department_name\nFROM employees e\nJOIN departments d ON e.emp_id = d.emp_id;<\/code><\/pre>\n\n\n\n
      \u8fd9\u6837\u53ef\u4ee5\u51cf\u5c11\u4ee3\u7801\u5197\u4f59\uff0c\u4f7f SQL \u8bed\u53e5\u66f4\u6e05\u6670\u3002<\/p>\n\n\n\n
      \n\n\n\n
      4. \u5728\u5b50\u67e5\u8be2\u4e2d\u4f7f\u7528\u522b\u540d<\/strong><\/h2>\n\n\n\n
      \u5728\u5b50\u67e5\u8be2\u4e2d\uff0c\u522b\u540d\u53ef\u4ee5\u7ed9\u4e34\u65f6\u8ba1\u7b97\u51fa\u6765\u7684\u8868\u8d77\u540d\uff0c\u4ee5\u4fbf\u540e\u7eed\u67e5\u8be2\u4f7f\u7528\uff1a<\/p>\n\n\n\n
      SELECT emp_name, total_salary\nFROM (\n    SELECT first_name || ' ' || last_name AS emp_name, salary * 12 AS total_salary\n    FROM employees\n) AS emp_summary\nWHERE total_salary > 70000;<\/code><\/pre>\n\n\n\n
      \u8fd9\u91cc emp_summary<\/code> \u4f5c\u4e3a\u5b50\u67e5\u8be2\u7684\u4e34\u65f6\u8868\u522b\u540d\uff0c\u53ef\u4ee5\u5728\u5916\u5c42\u67e5\u8be2\u4e2d\u4f7f\u7528\u3002<\/p>\n\n\n\n
      \n\n\n\n
      5. \u5728 CASE \u8bed\u53e5\u4e2d\u4f7f\u7528\u522b\u540d<\/strong><\/h2>\n\n\n\n
      SELECT first_name, last_name,\n       CASE \n           WHEN salary > 6000 THEN 'High'\n           WHEN salary BETWEEN 4000 AND 6000 THEN 'Medium'\n           ELSE 'Low'\n       END AS salary_level\nFROM employees;<\/code><\/pre>\n\n\n\n
      \u7ed3\u679c<\/strong>\uff1a<\/p>\n\n\n\n
      first_name<\/th>last_name<\/th>salary_level<\/th><\/tr><\/thead>
      Alice<\/td>Smith<\/td>Medium<\/td><\/tr>
      Bob<\/td>Johnson<\/td>High<\/td><\/tr>
      Charlie<\/td>Brown<\/td>High<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
      \n\n\n\n
      6. \u5728\u8ba1\u7b97\u5b57\u6bb5\u4e2d\u4f7f\u7528\u522b\u540d<\/strong><\/h2>\n\n\n\n
      SELECT first_name, last_name, salary, salary * 1.1 AS new_salary\nFROM employees;<\/code><\/pre>\n\n\n\n
      \u7ed3\u679c<\/strong>\uff1a<\/p>\n\n\n\n
      first_name<\/th>last_name<\/th>salary<\/th>new_salary<\/th><\/tr><\/thead>
      Alice<\/td>Smith<\/td>5000<\/td>5500<\/td><\/tr>
      Bob<\/td>Johnson<\/td>6000<\/td>6600<\/td><\/tr>
      Charlie<\/td>Brown<\/td>7000<\/td>7700<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
      \n\n\n\n
      7. \u5728 GROUP BY \u548c ORDER BY \u4e2d\u4f7f\u7528\u522b\u540d<\/strong><\/h2>\n\n\n\n
      \u522b\u540d \u4e0d\u80fd<\/strong> \u5728 GROUP BY<\/code> \u548c ORDER BY<\/code> \u4e2d\u76f4\u63a5\u4f7f\u7528\uff0c\u5fc5\u987b\u7528 \u5217\u7f16\u53f7\u6216\u539f\u5b57\u6bb5\u540d<\/strong>\u3002<\/p>\n\n\n\n
      SELECT first_name, COUNT(*) AS emp_count\nFROM employees\nGROUP BY first_name;<\/code><\/pre>\n\n\n\n
      \u4f46\u5728 ORDER BY<\/code> \u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528\u522b\u540d\uff1a<\/p>\n\n\n\n
      SELECT first_name, salary AS monthly_salary\nFROM employees\nORDER BY monthly_salary DESC;<\/code><\/pre>\n\n\n\n
      \n\n\n\n
      \u603b\u7ed3<\/strong><\/h2>\n\n\n\n
      \u65b9\u5f0f<\/th>\u8bed\u6cd5\u793a\u4f8b<\/th>\u4f5c\u7528<\/th><\/tr><\/thead>
      \u5217\u522b\u540d<\/strong><\/td>SELECT column_name AS alias_name FROM table;<\/code><\/td>\u8ba9\u67e5\u8be2\u7ed3\u679c\u66f4\u6e05\u6670<\/td><\/tr>
      \u8868\u522b\u540d<\/strong><\/td>SELECT e.column_name FROM table_name e;<\/code><\/td>\u8ba9 SQL \u8bed\u53e5\u66f4\u7b80\u6d01\uff0c\u5c24\u5176\u662f JOIN \u65f6<\/td><\/tr>
      \u5b50\u67e5\u8be2\u522b\u540d<\/strong><\/td>SELECT * FROM (SELECT ...) AS alias_name;<\/code><\/td>\u8ba9\u4e34\u65f6\u8868\u6709\u540d\u79f0\uff0c\u65b9\u4fbf\u5916\u5c42\u67e5\u8be2<\/td><\/tr>
      \u8ba1\u7b97\u5b57\u6bb5\u522b\u540d<\/strong><\/td>SELECT salary * 12 AS yearly_salary;<\/code><\/td>\u4e3a\u8ba1\u7b97\u7ed3\u679c\u8d4b\u540d\u79f0<\/td><\/tr>
      CASE \u8bed\u53e5\u522b\u540d<\/strong><\/td>CASE ... END AS alias_name<\/code><\/td>\u8ba9\u5206\u7c7b\u6570\u636e\u66f4\u76f4\u89c2<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
      \n\n\n\n
      \u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
      \u5728 PostgreSQL \u4e2d\uff0c\u522b\u540d\uff08Alias\uff09 \u4e3b\u8981\u7528\u4e8e\u7ed9 \u8868\uff08Table\uff09 \u6216 \u5217\uff08Column\uff09 \u8d4b\u4e88\u4e34 […]<\/p>\n","protected":false},"author":1,"featured_media":2664,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[78],"tags":[],"class_list":["post-2663","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\/2663","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=2663"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2663\/revisions"}],"predecessor-version":[{"id":2665,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2663\/revisions\/2665"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/2664"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=2663"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=2663"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=2663"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}