SQL笔记-建索引
一、说明
- Oracle:
-- 创建单列索引
CREATE INDEX index_name ON table_name(column_name);
-- 创建联合索引
CREATE INDEX index_name ON table_name(column1, column2, column3);
- MySQL:
-- 创建单列索引
ALTER TABLE table_name ADD INDEX index_name(column_name);
-- 创建联合索引
ALTER TABLE table_name ADD INDEX index_name(column1, column2, column3);
- SQL Server:
-- 创建单列索引
CREATE INDEX index_name ON table_name(column_name);
-- 创建联合索引
CREATE INDEX index_name ON table_name(column1, column2, column3);
- PostgreSQL:
-- 创建单列索引
CREATE INDEX index_name ON table_name(column_name);
-- 创建联合索引
CREATE INDEX index_name ON table_name(column1, column2, column3);
二、示例
- Oracle:
建表语句：
CREATE TABLE table1(
id NUMBER(10) PRIMARY KEY,
name VARCHAR2(50),
age NUMBER(3),
gender VARCHAR2(10),
address VARCHAR2(100)
);
CREATE TABLE table2(
id NUMBER(10) PRIMARY KEY,
table1_id NUMBER(10),
subject VARCHAR2(50),
score NUMBER(3)
);
ALTER TABLE table2 ADD FOREIGN KEY (table1_id) REFERENCES table1(id);
数据插入语句：
-- 插入 table1 数据
INSERT INTO table1(id, name, age, gender, address) VALUES(1, 'John', 25, 'Male', 'New York');
INSERT INTO table1(id, name, age, gender, address) VALUES(2, 'Mary', 30, 'Female', 'Los Angeles');
-- 插入 table2 数据
INSERT INTO table2(id, table1_id, subject, score) VALUES(1, 1, 'Math', 80);
INSERT INTO table2(id, table1_id, subject, score) VALUES(2, 1, 'English', 90);
INSERT INTO table2(id, table1_id, subject, score) VALUES(3, 2, 'Math', 85);
INSERT INTO table2(id, table1_id, subject, score) VALUES(4, 2, 'English', 95);
建立索引：
-- 对 table1 的 id 列建立索引
CREATE INDEX idx_table1_id ON table1(id);
-- 对 table2 的 table1_id 列建立索引
CREATE INDEX idx_table2_table1_id ON table2(table1_id);
- MySQL:
建表语句：
CREATE TABLE table1(
id INT(10) PRIMARY KEY,
name VARCHAR(50),
age INT(3),
gender VARCHAR(10),
address VARCHAR(100)
);
CREATE TABLE table2(
id INT(10) PRIMARY KEY,
table1_id INT(10),
subject VARCHAR(50),
score INT(3)
);
ALTER TABLE table2 ADD FOREIGN KEY (table1_id) REFERENCES table1(id);
数据插入语句：
-- 插入 table1 数据
INSERT INTO table1(id, name, age, gender, address) VALUES(1, 'John', 25, 'Male', 'New York');
INSERT INTO table1(id, name, age, gender, address) VALUES(2, 'Mary', 30, 'Female', 'Los Angeles');
-- 插入 table2 数据
INSERT INTO table2(id, table1_id, subject, score) VALUES(1, 1, 'Math', 80);
INSERT INTO table2(id, table1_id, subject, score) VALUES(2, 1, 'English', 90);
INSERT INTO table2(id, table1_id, subject, score) VALUES(3, 2, 'Math', 85);
INSERT INTO table2(id, table1_id, subject, score) VALUES(4, 2, 'English', 95);
建立索引：
-- 对 table1 的 id 列建立索引
ALTER TABLE table1 ADD INDEX idx_table1_id(id);
-- 对 table2 的 table1_id 列建立索引
ALTER TABLE table2 ADD INDEX idx_table2_table1_id(table1_id);
- SQL Server:
建表语句：
CREATE TABLE table1(
id INT PRIMARY KEY,
name VARCHAR(50),
age INT,
gender VARCHAR(10),
address VARCHAR(100)
);
CREATE TABLE table2(
id INT PRIMARY KEY,
table1_id INT,
subject VARCHAR(50),
score INT
);
ALTER TABLE table2 ADD FOREIGN KEY (table1_id) REFERENCES table1(id);
数据插入语句：
-- 插入 table1 数据
INSERT INTO table1(id, name, age, gender, address) VALUES(1, 'John', 25, 'Male', 'New York');
INSERT INTO table1(id, name, age, gender, address) VALUES(2, 'Mary', 30, 'Female', 'Los Angeles');
-- 插入 table2 数据
INSERT INTO table2(id, table1_id, subject, score) VALUES(1, 1, 'Math', 80);
INSERT INTO table2(id, table1_id, subject, score) VALUES(2, 1, 'English', 90);
INSERT INTO table2(id, table1_id, subject, score) VALUES(3, 2, 'Math', 85);
INSERT INTO table2(id, table1_id, subject, score) VALUES(4, 2, 'English', 95);
建立索引：
-- 对 table1 的 id 列建立索引
CREATE INDEX idx_table1_id ON table1(id);
-- 对 table2 的 table1_id 列建立索引
CREATE INDEX idx_table2_table1_id ON table2(table1_id);
- PostgreSQL:
建表语句：
CREATE TABLE table1(
id SERIAL PRIMARY KEY,
name VARCHAR(50),
age INT,
gender VARCHAR(10),
address VARCHAR(100)
);
CREATE TABLE table2(
id SERIAL PRIMARY KEY,
table1_id INT,
subject VARCHAR(50),
score INT
);
ALTER TABLE table2 ADD FOREIGN KEY (table1_id) REFERENCES table1(id);
数据插入语句：
-- 插入 table1 数据
INSERT INTO table1(name, age, gender, address) VALUES('John', 25, 'Male', 'New York');
INSERT INTO table1(name, age, gender, address) VALUES('Mary', 30, 'Female', 'Los Angeles');
-- 插入 table2 数据
INSERT INTO table2(table1_id, subject, score) VALUES(1, 'Math', 80);
INSERT INTO table2(table1_id, subject, score) VALUES(1, 'English', 90);
INSERT INTO table2(table1_id, subject, score) VALUES(2, 'Math', 85);
INSERT INTO table2(table1_id, subject, score) VALUES(2, 'English', 95);
建立索引：
-- 对 table1 的 id 列建立索引
CREATE INDEX idx_table1_id ON table1(id);
-- 对 table2 的 table1_id 列建立索引
CREATE INDEX idx_table2_table1_id ON table2(table1_id);