在两个表上执行左外部联接时,是否可以插入零而不是空?
假设我有这样一个查询:
SELECT * FROM (SELECT uID from Class) T1 LEFT OUTER JOIN (SELECT pID from University) T2 ON T1.uID = T2.pID CASE WHEN T1.uID IS NULL THEN 0 ELSE T1.uID END AS uID`
如果我错了就纠正我
比如:
SELECT * FROM (SELECT ifnull(uID,0) as uID from Class) T1 LEFT OUTER JOIN (SELECT ifnull(pID,0) as pID from University) T2 ON T1.uID = T2.pID
使用isNull(字段,0)如果字段为空,则插入零
CASE WHEN a.fieldname IS NULL THEN 0 ELSE a.fieldname END AS fieldname
