SELECT L.ID
FROM LINK L
WHERE L.LEFT = 0
AND L.RIGHT <> 0
UNION ALL
SELECT L.ID
FROM LINK L
WHERE L.LEFT <> 0
AND L.RIGHT = 01
已知在表link中 id是主键索引
请问能否优化该语句。
FROM LINK L
WHERE L.LEFT = 0
AND L.RIGHT <> 0
UNION ALL
SELECT L.ID
FROM LINK L
WHERE L.LEFT <> 0
AND L.RIGHT = 01
已知在表link中 id是主键索引
请问能否优化该语句。
AND L.RIGHT <> 0
建立位图索引
union
SELECT L.ID FROM LINK L WHERE L.RIGHT<0 and L.LEFT = 0)
union all
(SELECT L.ID FROM LINK L WHERE L.RIGHT>0 and L.LEFT = 01
union
SELECT L.ID FROM LINK L WHERE L.RIGHT<0 and L.LEFT = 01)
这是最高效的方式
不解,
SELECT L.ID FROM LINK L WHERE L.RIGHT>0 and L.LEFT = 0
union
SELECT L.ID FROM LINK L WHERE L.RIGHT<0 and L.LEFT = 0
和 SELECT L.ID FROM LINK L WHERE L.RIGHT<>0 and L.LEFT = 0 不一样吗?