例如:
SELECT ... FROM (SELECT ... FROM A表 a WHERE a.字段1 !="") c LEFT JOIN B表 b ON c.字段2=b.字段2
和
SELECT ... FROM (SELECT ... FROM A表 a ) c LEFT JOIN B表 b ON c.字段2=b.字段2 WHERE c.字段1 != ""
例如:
SELECT ... FROM (SELECT ... FROM A表 a WHERE a.字段1 !="") c LEFT JOIN B表 b ON c.字段2=b.字段2
和
SELECT ... FROM (SELECT ... FROM A表 a ) c LEFT JOIN B表 b ON c.字段2=b.字段2 WHERE c.字段1 != ""