sql - Where 子句案例陈述；ORA-00907: 缺少括号

Question

我有一个查询，当我运行它时，我收到错误消息ORA-00907: missing parenthesis。当我用x = g 和或y = g替换CASE语句时，它会按预期运行。

SELECT *
FROM
table1,
table2,
table3,
table4,
table5,
table6,
table7,
table8
WHERE
a = b and
c = d and
e = d and
CASE strfldvar
    WHEN 'BROKEN_ARROW' THEN (x = g)
    WHEN 'BROKEN_BOX'   THEN (y = g)
ELSE -1
end 
and
f = h and
i = j

我在这里做错了什么？

Answer 1

代替

CASE strfldvar
    WHEN 'BROKEN_ARROW' THEN (x = g)
    WHEN 'BROKEN_BOX'   THEN (y = g)
ELSE -1

拥有这个：

x=CASE strfldvar WHEN 'BROKEN_ARROW' THEN g ELSE x END
y=CASE strfldvar WHEN 'BROKEN_ARROW' THEN g ELSE y END

Answer 2

case is an expression, not a predicate (i.e condition) : it 'returns' a typed value and can not contain predicate as result (in the then parts). In your case (assuming else -1 means 'no match') :

AND g = CASE strfldvar
  WHEN 'BROKEN_ARROW' THEN x
  WHEN 'BROKEN_BOX'   THEN y 
  ELSE NULL -- never match, even if g is null
END

although I think it would be simpler to replace it with :

AND (
     (strfldvar = 'BROKEN_ARROW' AND x = g) 
  OR (strfldvar = 'BROKEN_BOX' AND y = g)
)

Answer 3

我会替换

CASE strfldvar
    WHEN 'BROKEN_ARROW' THEN (x = g)
    WHEN 'BROKEN_BOX'   THEN (y = g)
ELSE -1

经过

(CASE WHEN strfldvar = 'BROKEN_ARROW' and x = g then 1 
      WHEN strfldvar = 'BROKEN_BOX' and y = g then 1
      ELSE -1
      END) = 1