select t1.fieldname, t2.fieldname from tablename1 left join tablename2 t2 on t1.id = t2.id
兩個表的交集,就是把兩表的相同記錄先出來。select a.field1,a.field2,a.field3 from table1 a inner join table2 b on a.field1=b.field1 and a.field2=b.field2 and a.field3=b.field3......field1,field2,field3 .....相同的列
from tablename1
left join tablename2 t2 on t1.id = t2.id
对SQL表处理无效