【CXY】常用sql语句 -- mysql

CREATE TABLE t_test
(
id_ VARCHAR(32),
title_ VARCHAR(255),
content_ VARCHAR(2000),
create_time_ VARCHAR(25),
state_ VARCHAR(10)
)

INSERT INTO t_test  VALUES ('1', '标题','内容','2013-01-30','1')
INSERT INTO t_test (id_,title_,state_) VALUES ('2', '标题2','0')

DELETE FROM t_test WHERE id_='2'

UPDATE t_test SET title_ = '标题改',content_='内容改' WHERE id_='1'

SELECT * FROM t_test WHERE id_='1'
SELECT title_ AS 标题,content_ AS 内容 FROM t_test WHERE id_='1'
SELECT * FROM t_test LIMIT 2,3 //从序号2开始，查3条记录，做翻页最简单

ALTER TABLE t_test ADD click_num_ VARCHAR(10)

SELECT SUM(CAST(id_ AS DECIMAL)) FROM t_test

SELECT IFNULL(SUM(CAST(click_num_ AS DECIMAL)),0) FROM t_test

CREATE TABLE IF NOT EXISTS t_test
(
id_ VARCHAR(32) NOT NULL UNIQUE,
title_ VARCHAR(255),
content_ VARCHAR(2000),
create_time_ VARCHAR(25),
state_ VARCHAR(10)
)

SELECT DISTINCT title_,content_ FROM t_test1

SELECT * FROM information_schema.columns WHERE table_schema='cxy' AND table_name='t_test' AND column_name='title_';

DROP TABLE t_test

SELECT CONCAT(title_,':',content_) AS 标题文章 FROM t_test

SELECT LEFT(content_,2) FROM t_test
SELECT RIGHT(content_,2) FROM t_test
SELECT SUBSTRING(content_,2,1) FROM t_test

SELECT VERSION(),USER(),DATABASE();

SELECT	id_ AS id,'正常' AS 状态,(id_*1.1) AS 主键转换 FROM t_test;
#会出现异常数据，类似：3.3000000000000003
SELECT	id_ AS id,'正常' AS 状态,CONVERT((id_*1.1),DECIMAL(10,2)) AS 主键转换 FROM t_test;

#CAST(xxx  AS   类型) , CONVERT(xxx,类型)	SIGNED:整数
SELECT CONVERT('23.1',SIGNED);	#结果：23
SELECT CONVERT('23.9',SIGNED);	#结果：23
SELECT CONVERT('23.1',DECIMAL(4,2));	#DECIMAL(2+2,2)，第一个参数是小数点前和小数点后的和值，第二个参数是小数点后的值
SELECT LEFT(CONVERT(100.1,CHAR),2);

SELECT CAST('23.911' AS DECIMAL(4,2));	#结果：23.91

SELECT t_temp.标题,t_temp.内容 FROM
(SELECT id_, title_ AS 标题,content_ AS 内容 FROM t_test) AS t_temp;	#t_temp 就是临时表

#创建试图不能包含子查询
CREATE VIEW t_simple_test AS
SELECT SUM(id_) FROM t_test;

SELECT * FROM t_simple_test;

DROP VIEW t_simple_test;

#可以使用表别名 来简化长表明 可以直接写别名，也可以 使用as
SELECT t.id_,t.title_ FROM t_test t;
SELECT t.id_,t.title_ FROM t_test AS t;

# where 中的 and、or、not、between and/is null
SELECT * FROM t_test WHERE NOT(id_='1');
SELECT * FROM t_test WHERE title_ IS NOT NULL AND id_='2' OR id_='3';
SELECT * FROM t_test WHERE create_time_ BETWEEN '2012-12-01' AND '2013-01-31'

#having 能对分组后的数据进行筛选，尤其在使用聚集函数的时候
SELECT create_time_,SUM(click_num_) AS num FROM t_test
WHERE SUM(click_num_) > 2
GROUP BY create_time_ ;	#这个查询是会报错的

SELECT create_time_,SUM(click_num_) AS num FROM t_test
GROUP BY create_time_ HAVING num > 2;

#ORDER BY
SELECT * FROM t_test ORDER BY click_num_;	#从小到大
SELECT * FROM t_test ORDER BY click_num_ DESC;	#从大到小
SELECT * FROM t_test ORDER BY click_num_ ,id_;	#多排序

SELECT * FROM t_test WHERE  id_ != '1';
SELECT * FROM t_test WHERE  id_ <> '1';

SELECT * FROM t_test WHERE title_ IN('标题1','标题2');
SELECT * FROM t_test WHERE id_ IN(SELECT id_ FROM t_test WHERE click_num_ >3);
SELECT * FROM t_test WHERE id_ NOT IN(SELECT id_ FROM t_test WHERE click_num_ >3);

SELECT * FROM t_test WHERE title_ LIKE '标题_';
SELECT * FROM t_test WHERE title_ LIKE '%题%';