剔除不可见的面片提高渲染性能

文章目录

• union （并集）
• • union distinct
  • union all
• intersect(交集)
• • intersect all
  • intersect distinct
• except 差集
• • except distinct
  • except distinct
  • except all

union （并集）

union distinct

使用前提：a和c数据类型一致，b和d数据类型一致，查询的两个结果集列数也得相同

默认的union 即为union distinct

select a,b from table1
union
select c,d from table2;

union all

并集不去重

MySQL只支持union

intersect(交集)

intersect all

intersect distinct

except 差集

except distinct

except 差集

except distinct

except all