mysql-in關鍵字，分組查詢，分頁查詢

1. in關鍵字，組查詢

# 使用or來查詢的化，不方便而且參數一多比較傻
select * from users where id=1 or id=2 or id=4;
select * from users where id in(1,2,4)
select * from users where id not in (2,3) order by javascore ase;

2. 分組查詢 group by

如果一個查詢語句使用了group by，則后面的條件要使用having關鍵字

CREATE TABLE godds(
	id BIGINT(20) NOT NULL AUTO_INCREMENT PRIMARY KEY COMMENT '主鍵',
	goodName VARCHAR(40) COMMENT '商品名稱',
	goodCategory VARCHAR(20) COMMENT '商品種類'
)
RENAME TABLE godds TO goods

select * from goods group by goodCate having goodCate

3. 分頁查詢 limit

#goods表中有7條數據記錄，每頁顯示3條，總共可以分3頁
#獲取第一頁數據
SELECT * FROM goods LIMIT 0,3;
#獲取第二頁數據
SELECT *FROM goods LIMIT 3,3;
#獲取第三頁的數據
SELECT * FROM goods LIMIT 6,3;

SELECT * FROM goods LIMIT (pageNo-1)*pageSize,pageSize;