SELECT L.ID FROM LINK L, FORM F WHERE L.NUM <> 1 and L.ID = F.ID AND F.WAY = 20 AND同时 L.NUM <> 1 建议改为>1 OR <1
SELECT L.ID FROM LINK L, FORM F WHERE (L.NUM <1 or L.NUM> 1) AND L.ID = F.ID AND F.WAY = 20 这样么?感觉在where子句中 应该把 AND L.ID = F.ID 放在第一行然后才是(L.NUM <1 or L.NUM> 1)
SELECT L.ID FROM LINK L, FORM F WHERE AND L.ID = F.ID AND L.NUM <1 AND F.WAY = 20 union SELECT L.ID FROM LINK L, FORM F WHERE AND L.ID = F.ID AND L.NUM >1 AND F.WAY = 20 这是最高效的了
FROM LINK L, FORM F
WHERE L.NUM <> 1 and
L.ID = F.ID AND F.WAY = 20 AND同时 L.NUM <> 1 建议改为>1 OR <1
SELECT L.ID
FROM LINK L, FORM F
WHERE (L.NUM <1 or L.NUM> 1)
AND L.ID = F.ID
AND F.WAY = 20 这样么?感觉在where子句中 应该把 AND L.ID = F.ID 放在第一行然后才是(L.NUM <1 or L.NUM> 1)
LINK表的ID,NUM字段分别建索引.
FORM表的ID,WAY字段建索引.
现在的情况是只在Link表的id列 建立索引
为何不建其他的索引呢?
SELECT L.ID
FROM LINK L, FORM F
WHERE
AND L.ID = F.ID
AND L.NUM <1
AND F.WAY = 20
union
SELECT L.ID
FROM LINK L, FORM F
WHERE
AND L.ID = F.ID
AND L.NUM >1
AND F.WAY = 20 这是最高效的了