MYSQL中DML与DDL常用语句小结

SELECT column1, column2, ...
FROM table_name
WHERE condition;

INSERT INTO table_name (column1, column2, ...)
VALUES (value1, value2, ...);

-- 单个
INSERT INTO employees(id, first_name, last_name, gender, hire_date, dept_id)
VALUES (101, 'John', 'Doe', 'M', '2020-01-01', 1);
-- 批量插入
INSERT INTO employees(id, first_name, last_name, gender, hire_date, dept_id)
VALUES (101, 'John', 'Doe', 'M', '2020-01-01', 1),
       (102, 'Jane', 'Doe', 'F', '2020-02-01', 2),
       (200, 'Alex', 'Lee', 'M', '2020-12-01', 3);
 
-- 使用 INSERT INTO ... SELECT ... 语句插入数据
INSERT INTO employees(id, first_name, last_name, gender, hire_date, dept_id)
SELECT id, first_name, last_name, gender, hire_date, dept_id
FROM temp_employees;

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

DELETE FROM table_name
WHERE condition;

CREATE TABLE table_name (
    column1 data_type constraints,
    column2 data_type constraints,
    ...
    table_constraints
);

ALTER TABLE table_name action;

-- 往user表中增加一个名为address的字段，规定了字段的类型，默认值以及注释，并放在了name字段后面。
ALTER TABLE user ADD COLUMN address varchar(256) DEFAULT '' COMMENT '字段注释' AFTER name;
-- 修改
ALTER TABLE user MODIFY COLUMN address varchar(256) DEFAULT '' COMMENT '字段注释';
-- 删除
ALTER TABLE user DROP COLUMN address;

DROP TABLE table_name;

CREATE INDEX index_name
ON table_name (column1, column2, ...);

CREATE INDEX idx_employee_dept_id ON employees(dept_id);

DROP INDEX index_name
ON table_name;

DROP INDEX idx_employee_dept_id ON employees;

-- 服务器
show variables like 'character_set_server';
show variables like 'collation_server';
-- 数据库
show variables like 'character_set_database';
show variables like 'collation_database';
-- 表
SHOW FULL COLUMNS FROM table_name;

-- 单独给表设置
ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;