mysql之谓词like/in/between/exist

################
##谓词
#like /between /is null/is not null/in/exists
################
show databases;
use xscj;
CREATE TABLE SampleLike (
 strcol VARCHAR(6) NOT NULL,  PRIMARY KEY (strcol));

START TRANSACTION; 
INSERT INTO SampleLike (strcol) VALUES ('abcddd'); 
INSERT INTO SampleLike (strcol) VALUES ('dddabc'); 
INSERT INTO SampleLike (strcol) VALUES ('abdddc'); 
INSERT INTO SampleLike (strcol) VALUES ('abcdd'); 
INSERT INTO SampleLike (strcol) VALUES ('ddabc'); 
INSERT INTO SampleLike (strcol) VALUES ('abddc');
COMMIT;

##like  
-- %代表0个及以上的任意字符串 
-- _代表任意一个字符
-- 1.ddd%前方一致查询
select * from SampleLike
where strcol like 'ddd%';  
-- 2.%ddd%中间一致查询（包括前方后方）
select * from SampleLike
where strcol like '%ddd%'; 
-- 3.%ddd后方一致
select * from SampleLike
where strcol like '%ddd';   

## between的结果包含临界值  
select product_name, sale_price from product
where sale_price between 100 and 1000;

## is null/is not null 选取某些值为Null的数据 
select product_name, sale_price from product
where purchase_price is null;

## in (or的简便用法）/not in
#笨拙用法 
select product_name,purchase_price
from product 
where purchase_price = 320
or    purchase_price = 500
or    purchase_price = 5000;
#简单用法 
select product_name,purchase_price
from product
where purchase_price in (320,500,5000);

-- 1.在使用in/not in的时候是无法取出null数据的，null数据还是需要is null/is not null
-- 2.in(not in)有其他谓词所没有的用法，就是可以使用子查询作为参数 

CREATE TABLE ShopProduct (
shop_id    CHAR(4) NOT NULL, 
shop_name  VARCHAR(200) NOT NULL, 
product_id CHAR(4)  NOT NULL, 
quantity   INTEGER NOT NULL, 
PRIMARY KEY (shop_id, product_id));
start TRANSACTION; 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000A', '东京', '0001', 30); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000A', '东京', '0002', 50); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000A', '东京', '0003', 15); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000B', '名古屋', '0002', 30); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000B', '名古屋', '0003', 120); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000B', '名古屋', '0004', 20); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000B', '名古屋', '0006', 10); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000B', '名古屋', '0007', 40); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000C', '大阪', '0003', 20); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000C', '大阪', '0004', 50); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000C', '大阪', '0006', 90); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000C', '大阪', '0007', 70); 
INSERT INTO ShopProduct (shop_id, shop_name, product_id, quantity) VALUES ('000D', '福冈', '0001', 100);
COMMIT;

select product_name,sale_price from product
where  product_id in (select product_id from shopproduct
                      where shop_name = "大阪");  
                      
                      
## exist/not exist 通常指定关联子查询作为exist的参数 
select product_name,sale_price 
from product as p
where exists (select * from shopproduct as sp
              where sp.shop_name = '大阪'
              and sp.product_id = p.product_id);
-- 大家可以吧exist的子查询中select *当做一种习惯。
--  因为exist值关心记录是否存在，因此返回哪些列都没有关系。
-- exist只会判断是否满足子查询中where子句指定的条件（ sp.shop_name = '大阪'
--              and sp.product_id = p.product_id)，只有存在这样的记录才返回真 
-- 其实exist后面就是一张记录表啦