{"id":2651,"date":"2025-03-12T23:30:40","date_gmt":"2025-03-12T15:30:40","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=2651"},"modified":"2025-03-12T23:30:40","modified_gmt":"2025-03-12T15:30:40","slug":"postgresql-%e7%ba%a6%e6%9d%9f%ef%bc%88constraints%ef%bc%89%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/03\/12\/postgresql-%e7%ba%a6%e6%9d%9f%ef%bc%88constraints%ef%bc%89%e8%af%a6%e8%a7%a3\/","title":{"rendered":"PostgreSQL \u7ea6\u675f\uff08Constraints\uff09\u8be6\u89e3"},"content":{"rendered":"\n

PostgreSQL\u7ea6\u675f\uff08Constraints\uff09\u7528\u4e8e\u786e\u4fdd\u6570\u636e\u5e93\u6570\u636e\u7684\u5b8c\u6574\u6027\u548c\u4e00\u81f4\u6027\u3002PostgreSQL \u63d0\u4f9b\u4e86\u591a\u79cd\u7ea6\u675f\u7c7b\u578b\uff0c\u5305\u62ec NOT NULL<\/code>\u3001UNIQUE<\/code>\u3001PRIMARY KEY<\/code>\u3001FOREIGN KEY<\/code>\u3001CHECK<\/code>\u3001DEFAULT<\/code> \u548c EXCLUSION<\/code> \u7ea6\u675f\u3002<\/p>\n\n\n\n

\n\n\n\n

1. NOT NULL \u7ea6\u675f<\/strong><\/h2>\n\n\n\n

\u7528\u4e8e\u786e\u4fdd\u67d0\u5217\u7684\u503c\u4e0d\u80fd\u4e3a NULL<\/code>\uff0c\u9002\u7528\u4e8e\u5173\u952e\u6570\u636e\u5b57\u6bb5\u3002<\/p>\n\n\n\n

1.1 \u8bed\u6cd5<\/strong><\/h3>\n\n\n\n
CREATE TABLE users (\n    id SERIAL PRIMARY KEY,\n    name VARCHAR(100) NOT NULL\n);<\/code><\/pre>\n\n\n\n
1.2 \u793a\u4f8b<\/strong><\/h3>\n\n\n\n
INSERT INTO users (id, name) VALUES (1, NULL);\n-- \u62a5\u9519\uff1a\u8fdd\u53cd NOT NULL \u7ea6\u675f<\/code><\/pre>\n\n\n\n
1.3 \u5220\u9664 NOT NULL \u7ea6\u675f<\/strong><\/h3>\n\n\n\n
ALTER TABLE users ALTER COLUMN name DROP NOT NULL;<\/code><\/pre>\n\n\n\n
\n\n\n\n
2. UNIQUE \u7ea6\u675f<\/strong><\/h2>\n\n\n\n
\u786e\u4fdd\u67d0\u5217\u6216\u591a\u4e2a\u5217\u7684\u503c\u5728\u8868\u4e2d\u662f\u552f\u4e00\u7684\u3002<\/p>\n\n\n\n
2.1 \u8bed\u6cd5<\/strong><\/h3>\n\n\n\n
CREATE TABLE users (\n    id SERIAL PRIMARY KEY,\n    email VARCHAR(255) UNIQUE\n);<\/code><\/pre>\n\n\n\n
2.2 \u590d\u5408 UNIQUE \u7ea6\u675f<\/strong><\/h3>\n\n\n\n
CREATE TABLE employees (\n    first_name VARCHAR(50),\n    last_name VARCHAR(50),\n    UNIQUE (first_name, last_name)\n);<\/code><\/pre>\n\n\n\n
2.3 \u8fdd\u53cd UNIQUE \u7ea6\u675f\u793a\u4f8b<\/strong><\/h3>\n\n\n\n
INSERT INTO users (email) VALUES ('user@example.com');\nINSERT INTO users (email) VALUES ('user@example.com');\n-- \u62a5\u9519\uff1a\u8fdd\u53cd UNIQUE \u7ea6\u675f<\/code><\/pre>\n\n\n\n
2.4 \u5220\u9664 UNIQUE \u7ea6\u675f<\/strong><\/h3>\n\n\n\n
ALTER TABLE users DROP CONSTRAINT users_email_key;<\/code><\/pre>\n\n\n\n
\n\n\n\n
3. PRIMARY KEY \u7ea6\u675f<\/strong><\/h2>\n\n\n\n
PRIMARY KEY<\/code> \u7ea6\u675f\u7531 UNIQUE<\/code> \u548c NOT NULL<\/code> \u7ec4\u5408\u800c\u6210\uff0c\u6bcf\u5f20\u8868\u53ea\u80fd\u6709\u4e00\u4e2a\u4e3b\u952e\u3002<\/p>\n\n\n\n
3.1 \u8bed\u6cd5<\/strong><\/h3>\n\n\n\n
CREATE TABLE orders (\n    id SERIAL PRIMARY KEY,\n    order_number VARCHAR(50) NOT NULL UNIQUE\n);<\/code><\/pre>\n\n\n\n
3.2 \u590d\u5408\u4e3b\u952e<\/strong><\/h3>\n\n\n\n
CREATE TABLE order_items (\n    order_id INT,\n    product_id INT,\n    PRIMARY KEY (order_id, product_id)\n);<\/code><\/pre>\n\n\n\n
3.3 \u5220\u9664 PRIMARY KEY<\/strong><\/h3>\n\n\n\n
ALTER TABLE orders DROP CONSTRAINT orders_pkey;<\/code><\/pre>\n\n\n\n
\n\n\n\n
4. FOREIGN KEY \u7ea6\u675f<\/strong><\/h2>\n\n\n\n
FOREIGN KEY<\/code> \u7ea6\u675f\u7528\u4e8e\u7ef4\u62a4\u8868\u4e0e\u8868\u4e4b\u95f4\u7684\u5173\u7cfb\uff0c\u786e\u4fdd\u5f15\u7528\u7684\u503c\u5728\u7236\u8868\u4e2d\u5b58\u5728\u3002<\/p>\n\n\n\n
4.1 \u8bed\u6cd5<\/strong><\/h3>\n\n\n\n
CREATE TABLE users (\n    id SERIAL PRIMARY KEY\n);\n\nCREATE TABLE orders (\n    id SERIAL PRIMARY KEY,\n    user_id INT REFERENCES users(id) ON DELETE CASCADE\n);<\/code><\/pre>\n\n\n\n
4.2 \u7ea7\u8054\u5220\u9664\uff08ON DELETE CASCADE\uff09<\/strong><\/h3>\n\n\n\n
\u5982\u679c users<\/code> \u8868\u7684\u67d0\u6761\u8bb0\u5f55\u88ab\u5220\u9664\uff0corders<\/code> \u8868\u4e2d\u5173\u8054\u7684\u6570\u636e\u4e5f\u4f1a\u88ab\u5220\u9664\u3002<\/p>\n\n\n\n
DELETE FROM users WHERE id = 1;\n-- \u8be5\u7528\u6237\u7684\u6240\u6709\u8ba2\u5355\u4e5f\u4f1a\u88ab\u5220\u9664<\/code><\/pre>\n\n\n\n
4.3 \u5220\u9664 FOREIGN KEY<\/strong><\/h3>\n\n\n\n
ALTER TABLE orders DROP CONSTRAINT orders_user_id_fkey;<\/code><\/pre>\n\n\n\n
\n\n\n\n
5. CHECK \u7ea6\u675f<\/strong><\/h2>\n\n\n\n
CHECK<\/code> \u7ea6\u675f\u7528\u4e8e\u9650\u5236\u5217\u7684\u503c\u7b26\u5408\u67d0\u4e2a\u6761\u4ef6\u3002<\/p>\n\n\n\n
5.1 \u8bed\u6cd5<\/strong><\/h3>\n\n\n\n
CREATE TABLE products (\n    id SERIAL PRIMARY KEY,\n    price DECIMAL CHECK (price > 0)\n);<\/code><\/pre>\n\n\n\n
5.2 \u590d\u6742 CHECK \u7ea6\u675f<\/strong><\/h3>\n\n\n\n
CREATE TABLE employees (\n    id SERIAL PRIMARY KEY,\n    age INT CHECK (age >= 18 AND age <= 65)\n);<\/code><\/pre>\n\n\n\n
5.3 \u8fdd\u53cd CHECK \u7ea6\u675f\u793a\u4f8b<\/strong><\/h3>\n\n\n\n
INSERT INTO employees (age) VALUES (17);\n-- \u62a5\u9519\uff1a\u8fdd\u53cd CHECK \u7ea6\u675f<\/code><\/pre>\n\n\n\n
5.4 \u5220\u9664 CHECK \u7ea6\u675f<\/strong><\/h3>\n\n\n\n
ALTER TABLE employees DROP CONSTRAINT employees_age_check;<\/code><\/pre>\n\n\n\n
\n\n\n\n
6. DEFAULT \u7ea6\u675f<\/strong><\/h2>\n\n\n\n
\u7528\u4e8e\u6307\u5b9a\u9ed8\u8ba4\u503c\u3002<\/p>\n\n\n\n
6.1 \u8bed\u6cd5<\/strong><\/h3>\n\n\n\n
CREATE TABLE users (\n    id SERIAL PRIMARY KEY,\n    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP\n);<\/code><\/pre>\n\n\n\n
6.2 \u4f7f\u7528 DEFAULT<\/strong><\/h3>\n\n\n\n
INSERT INTO users (id) VALUES (1);\nSELECT * FROM users;\n-- created_at \u5c06\u81ea\u52a8\u586b\u5145\u5f53\u524d\u65f6\u95f4<\/code><\/pre>\n\n\n\n
6.3 \u4fee\u6539 DEFAULT<\/strong><\/h3>\n\n\n\n
ALTER TABLE users ALTER COLUMN created_at SET DEFAULT NOW();<\/code><\/pre>\n\n\n\n
6.4 \u5220\u9664 DEFAULT<\/strong><\/h3>\n\n\n\n
ALTER TABLE users ALTER COLUMN created_at DROP DEFAULT;<\/code><\/pre>\n\n\n\n
\n\n\n\n
7. EXCLUSION \u7ea6\u675f<\/strong><\/h2>\n\n\n\n
EXCLUSION<\/code> \u7ea6\u675f\u7528\u4e8e\u786e\u4fdd\u6570\u636e\u8303\u56f4\u6216\u8868\u8fbe\u5f0f\u7684\u552f\u4e00\u6027\uff0c\u5e38\u7528\u4e8e RANGE<\/code> \u6570\u636e\u7c7b\u578b\u3002<\/p>\n\n\n\n
7.1 \u8bed\u6cd5<\/strong><\/h3>\n\n\n\n
CREATE TABLE room_reservations (\n    id SERIAL PRIMARY KEY,\n    room_id INT,\n    period TSRANGE,\n    EXCLUDE USING GIST (room_id WITH =, period WITH &&)\n);<\/code><\/pre>\n\n\n\n
7.2 \u4f5c\u7528<\/strong><\/h3>\n\n\n\n
    \n
  • room_id WITH =<\/code> \u786e\u4fdd room_id<\/code> \u4e0d\u80fd\u91cd\u590d\u3002<\/li>\n\n\n\n
  • period WITH &&<\/code> \u786e\u4fdd\u65f6\u95f4\u8303\u56f4\u4e0d\u80fd\u91cd\u53e0\u3002<\/li>\n<\/ul>\n\n\n\n
    7.3 \u5220\u9664 EXCLUSION \u7ea6\u675f<\/strong><\/h3>\n\n\n\n
    ALTER TABLE room_reservations DROP CONSTRAINT room_reservations_exclusion;<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    8. \u6dfb\u52a0\u3001\u5220\u9664\u548c\u4fee\u6539\u7ea6\u675f<\/strong><\/h2>\n\n\n\n
    8.1 \u6dfb\u52a0 NOT NULL \u7ea6\u675f<\/strong><\/h3>\n\n\n\n
    ALTER TABLE users ALTER COLUMN name SET NOT NULL;<\/code><\/pre>\n\n\n\n
    8.2 \u6dfb\u52a0 UNIQUE \u7ea6\u675f<\/strong><\/h3>\n\n\n\n
    ALTER TABLE users ADD CONSTRAINT unique_email UNIQUE (email);<\/code><\/pre>\n\n\n\n
    8.3 \u6dfb\u52a0 CHECK \u7ea6\u675f<\/strong><\/h3>\n\n\n\n
    ALTER TABLE employees ADD CONSTRAINT check_age CHECK (age >= 18);<\/code><\/pre>\n\n\n\n
    8.4 \u5220\u9664\u7ea6\u675f<\/strong><\/h3>\n\n\n\n
    ALTER TABLE users DROP CONSTRAINT unique_email;<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    \u603b\u7ed3<\/strong><\/h2>\n\n\n\n
    \u7ea6\u675f\u7c7b\u578b<\/th>\u4f5c\u7528<\/th><\/tr><\/thead>
    NOT NULL<\/code><\/td>\u786e\u4fdd\u5217\u503c\u4e0d\u80fd\u4e3a\u7a7a<\/td><\/tr>
    UNIQUE<\/code><\/td>\u786e\u4fdd\u5217\u503c\u552f\u4e00<\/td><\/tr>
    PRIMARY KEY<\/code><\/td>\u552f\u4e00\u4e14\u975e\u7a7a\uff0c\u6bcf\u4e2a\u8868\u53ea\u80fd\u6709\u4e00\u4e2a<\/td><\/tr>
    FOREIGN KEY<\/code><\/td>\u7ef4\u62a4\u8868\u4e4b\u95f4\u7684\u5173\u7cfb<\/td><\/tr>
    CHECK<\/code><\/td>\u9650\u5236\u5217\u503c\u7684\u8303\u56f4\u6216\u6761\u4ef6<\/td><\/tr>
    DEFAULT<\/code><\/td>\u6307\u5b9a\u5217\u7684\u9ed8\u8ba4\u503c<\/td><\/tr>
    EXCLUSION<\/code><\/td>\u786e\u4fdd\u6570\u636e\u8303\u56f4\u6216\u8868\u8fbe\u5f0f\u7684\u552f\u4e00\u6027<\/td><\/tr><\/tbody><\/table><\/figure>\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":"
    PostgreSQL\u7ea6\u675f\uff08Constraints\uff09\u7528\u4e8e\u786e\u4fdd\u6570\u636e\u5e93\u6570\u636e\u7684\u5b8c\u6574\u6027\u548c\u4e00\u81f4\u6027\u3002PostgreSQL \u63d0 […]<\/p>\n","protected":false},"author":1,"featured_media":2652,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[78],"tags":[],"class_list":["post-2651","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\/2651","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=2651"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2651\/revisions"}],"predecessor-version":[{"id":2653,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2651\/revisions\/2653"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/2652"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=2651"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=2651"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=2651"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}