目录
- 一、基本信息查看
- 1. 表描述
- 二、表操作
- 1. 查看建表语句
- 2.查看表
- 3. 创建表
- 4. 更新表
- 5. 删除表
- 6. 重命名表
- 三、索引操作
- 1. 查看索引
- 2. 创建索引
- 3. 修改索引
- 4. 删除索引
- 四、记录操作
- 1. 查询记录
- 2. 添加记录
- 3. 更新记录
- 4. 删除记录
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_name2WHERE 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
SELECTtable_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`,
CASEWHEN 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`