sql提高

sql提高

集合

union all 合集，且重复

select * from T_OWNERS
union all
select * from t_userAddress

union 合集,去重复

// 字段位置、个数必须一致，不一致就容易报错
select * from T_OWNERS
union 
select * from t_userAddress

intersect 交集，操作级别比union高

select * from T_OWNERS
intersect 
select * from t_userAddress

except 差集