mysql 脚本

# 创建新表并插入老表数据
create table xxx_bak select * from xxx

# 多表关联update
update xxx x 
join yyy y on y.id = x.id
set x.c = 'c'
where x.d = 'd'

# 多表关联delete
delete x
from xxx x
join yyy y on y.id = x.id
where x.c = ''

# case when 两种用法
# 简单函数 
CASE [col_name] WHEN [value1] THEN [result1]…ELSE [default] END
# 搜索函数 
CASE WHEN [expr] THEN [result1]…ELSE [default] END