目录
一、基本信息查看
1. 表描述
DESCRIBE `table_name`;
二、表操作
1. 查看建表语句
SHOW CREATE TABLE `table_name`;
2.查看表
SHOW TABLES;
3. 创建表
CREATE TABLE `table_name` (
`c_id` int(11) unsigned NOT NULL AUTO_INCREMENT COMMENT '唯一ID',
`c_is_deleted` tinyint(1) NOT NULL DEFAULT '0' COMMENT '逻辑删除',
`c_update_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '更新时间',
`c_create_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
PRIMARY KEY (`c_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='table_name'
CREATE TABLE IF NOT EXISTS `table_name` (
`c_id` bigint(20) unsigned NOT NULL COMMENT '唯一ID',
`c_uid` char(11) NOT NULL DEFAULT '' COMMENT 'uid列',
`c_char` char(11) NOT NULL DEFAULT '' COMMENT 'char列',
`c_varchar1` varchar(30) NOT NULL DEFAULT '' COMMENT 'varchar列',
`c_varchar2` varchar(300) CHARACTER SET utf8mb4 NOT NULL DEFAULT '' COMMENT 'varchar列，单独设置字符集',
`c_text` text CHARACTER SET utf8mb4 NOT NULL COMMENT 'text列，单独设置字符集',
`c_tinyint` tinyint(1) NOT NULL DEFAULT '0' COMMENT 'tinyint，当枚举用(0A 1B 2C)',
`c_enum` enum('0','1') NOT NULL DEFAULT '0' COMMENT 'enum，枚举用',
`c_json` json NOT NULL COMMENT 'json类型列',
`c_is_deleted` tinyint(1) NOT NULL DEFAULT '0' COMMENT '逻辑删除',
`c_update_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '更新时间',
`c_create_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
PRIMARY KEY (`c_id`),
KEY `inx_c_uid` (`c_uid`) USING BTREE,
UNIQUE KEY `udx_c1_c2` (`c_char`,`c_tinyint`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='table_name';
4. 更新表
- 增加列
ALTER TABLE `table_name` ADD `c_column` tinyint(1) not null DEFAULT 0 COMMENT '新增列';
- 修改列
ALTER TABLE `table_name` MODIFY COLUMN `c_varchar1` VARCHAR ( 300 ) NOT NULL DEFAULT '' COMMENT '标识符' AFTER `c_varchar2`;
- 删除列
ALTER TABLE `table_name` DROP COLUMN `c_column`;
5. 删除表
DROP TABLE if EXISTS `table_name`;
6. 重命名表
RENAME TABLE `table_name` TO `table_name_2`;
三、索引操作
1. 查看索引
SHOW INDEX FROM table_name [FROM db_name]
2. 创建索引
- 语法
CREATE [UNIQUE|FULLTEXT|SPATIAL] INDEX index_name
[USING index_type]
ON table_name (index_col_name, ...)
CREATE UNIQUE INDEX idx_uid ON `table_name` (`c_uid`);
-- TEXT和BLOB要指定长度
CREATE UNIQUE INDEX idx_text ON `table_name` (`c_text`(6));
ALTER TABLE方式
ALTER TABLE table_name
ADD [UNIQUE|FULLTEXT|SPATIAL] INDEX index_name (index_col_name,...) [USING index_type]
ALTER TABLE `table_name` ADD PRIMARY KEY ( `c_uid` )
ALTER TABLE `table_name` ADD INDEX `udx_c1_c2` ( `c_char`(n), `c_tinyint` ) USING BTREE;
3. 修改索引
ALTER TABLE `table_name` DROP INDEX `udx_c1_c2`,
ADD INDEX `udx_c1_c2` ( `c_char`, `c_tinyint`, `c_is_deleted` ) USING HASH;
4. 删除索引
ALTER TABLE table_name DROP PRIMARY KEY;
DROP INDEX `idx_name` ON `table_name`;
ALTER TABLE `table_name` DROP INDEX `udx_c1_c2`;
四、记录操作
1. 查询记录
- 简单查询
子句顺序：SELETC、 FROM、 WHERE、 GROUP BY、 HAVING、 ORDER BY、 LIMIT
SELECT * FROM table_name WHERE ... ORDER BY c_column1,c_column2 DESC;
- 模糊查询
特殊字符要转义%_
SELECT * FROM table_name WHERE c_column LIKE CONCAT('first','second','third');
SELECT * FROM table_name WHERE c_column LIKE CONCAT('%','_','%');
-
分组查询
WHERE过滤行,HAVING过滤分组
SELECT GROUP_CONCAT(c_column) FROM table_name WHERE c_is_deleted=0 GROUP BY c_column1, c_column2 HAVING COUNT(c_column3) >= 2;
-- 可能报错：incompatible with sql_mode=only_full_group_by
SELECT GROUP_CONCAT(c_column) FROM table_name WHERE c_is_deleted=0 GROUP BY c_column1, c_column2 HAVING COUNT(c_column3) >= 2 ORDER BY c_order DESC;
SELECT GROUP_CONCAT(c_id),COUNT(*) FROM table_name GROUP BY c_type WITH ROLLUP;
-
分页查询
检索出来的第一行为行0而不是行1。
-- 查询两条记录，开始行1
SELECT * FROM table_name LIMIT 1, 2;
- 计算字段和函数
（1）计算字段
SELECT 1+1 AS result;
SELECT CONCAT('first', c_column, 'third') AS c_alias_name FROM table_name;
SELECT CONCAT('first', TRIM(c_column), 'third') AS c_alias_name FROM table_name;
（2）处理函数
SELECT UUID() AS `uid`;
SELECT UPPER('a');
SELECT DATE(c_create_time) AS `date`, TIME(c_create_time) AS `time` FROM table_name;
（3）聚集函数
SELECT COUNT( * ),
MIN( c_column ),
MAX( c_column ),
AVG( c_column )
FROM table_name;
SELECT SUM( c_column1 * c_column2 )
FROM table_name;
- 子查询
SELECT *
FROM table_name1
WHERE c_column IN ( SELECT c_column
FROM table_name2
WHERE c_is_deleted = 1 );
-- 计算字段作为子查询
SELECT table_name1.c_name,
( SELECT COUNT( * )
FROM table_name2
WHERE table_name2.c_key = table_name1.c_key ) AS nums
FROM table_name1
WHERE c_is_deleted = 0;
- 联结查询
(1) 自联结
SELECT t1.c_id, t1.c_name
FROM table_name AS t1, table_name AS t2
WHERE t1.c_id = t2.c_id
AND t2.c_key = '';
(2) 自然联结
SELECT t1.c_id, t1.c_name
FROM table_name1 AS t1, table_name2 AS t2
WHERE t1.c_id = t2.c_id
AND t2.c_key = '';
(3) 外部联结
SELECT
table_name1.c_id,
table_name1.c_name,
table_name2.c_name
FROM table_name1
LEFT JOIN table_name2 ON table_name2.c_key = table_name1.c_key
WHERE ...;
- 查询结果
case when then else end用法
(1) 语法
--简单Case函数
CASE sex
WHEN '1' THEN '男'
WHEN '2' THEN '女'
ELSE '其他'
END
--Case搜索函数,
CASE
WHEN sex = '1' THEN '男'
WHEN sex = '2' THEN '女'
ELSE '其他'
END
(2) 示例
SELECT `name`,
CASE `name`
WHEN 'sam' THEN 'yong'
WHEN 'lee' THEN 'handsome'
ELSE 'good'
END AS `alias`
FROM `table_name`;
SELECT `name`,
CASE
WHEN birthday < '1981' THEN 'old'
WHEN birthday > '1988' THEN 'yong'
ELSE 'ok'
END AS `yorn`
FROM `table_name`;
2. 添加记录
- 简单插入
INSERT INTO table_name ( column1, column2 ) VALUES ( value1, value2 );
- 批量插入
INSERT INTO table_name
( column1, column2 )
VALUES
( value1, value2 ),
( value1, value2 );
INSERT SELECT插入
INSERT INTO table_name ( column1, column2 )
SELECT column1, column2
FROM table_name
WHERE c_id=1;
3. 更新记录
UPDATE `table_name`
SET
`c_varchar1` = 'string',
`c_update_time` = CURRENT_TIMESTAMP
WHERE `c_id` = 1;
4. 删除记录
- DELETE方式
DELETE FROM `table_name` WHERE `c_id`=1;
- TRUNCATE方式-清空表-慎用
-- 删除原表再新建表
TRUNCATE TABLE `table_name`