ORA-00908缺失关键字错误：PL/SQL Developer中SQL语句求助

错误原因 #

Oracle的CASE表达式不支持直接返回布尔逻辑表达式（比如原语句中A.C07FECHADE >= ... AND A.C07FECHADE <= ...这种组合条件）。WHERE子句要求的是布尔结果，但CASE在这里必须返回单一值（日期、数字等）后再做比较，原写法违反了语法规则，因此触发ORA-00908错误。

解决方案 #

方案1：拆分条件为AND/OR组合逻辑 #

直接把CASE的分支逻辑拆成两个独立的条件块，用OR连接，逻辑更直观：

SELECT COUNT(0) AS CANT, 
       C.C06NOMBRE AS CONSOLIDADORA
FROM T07OBLIGACION A
JOIN T06EMPRESA B ON A.C07EMPRESA = B.C06IDEMPRESA AND A.C07CODSUCURSAL = B.C06CODSUCURSAL
JOIN T06EMPRESA C ON C.C06IDEMPRESA = B.C06IDPAGCON AND C.C06CODSUCURSAL = B.C06SUCURSALCON
WHERE 
  (B.C06FECHACOR <= SYSDATE 
   AND A.C07FECHADE >= ADD_MONTHS(B.C06FECHACOR, -2) 
   AND A.C07FECHADE <= ADD_MONTHS(B.C06FECHACOR, -1) - 1)
  OR
  (B.C06FECHACOR > SYSDATE 
   AND A.C07FECHADE >= ADD_MONTHS(B.C06FECHACOR, -1) 
   AND A.C07FECHADE <= B.C06FECHACOR - 1)
GROUP BY C.C06NOMBRE

方案2：调整CASE返回值，配合BETWEEN使用 #

让CASE分别返回日期范围的上下限，再用BETWEEN做范围判断：

SELECT COUNT(0) AS CANT, 
       C.C06NOMBRE AS CONSOLIDADORA
FROM T07OBLIGACION A
JOIN T06EMPRESA B ON A.C07EMPRESA = B.C06IDEMPRESA AND A.C07CODSUCURSAL = B.C06CODSUCURSAL
JOIN T06EMPRESA C ON C.C06IDEMPRESA = B.C06IDPAGCON AND C.C06CODSUCURSAL = B.C06SUCURSALCON
WHERE 
  A.C07FECHADE BETWEEN 
    CASE WHEN B.C06FECHACOR <= SYSDATE THEN ADD_MONTHS(B.C06FECHACOR, -2) ELSE ADD_MONTHS(B.C06FECHACOR, -1) END
    AND
    CASE WHEN B.C06FECHACOR <= SYSDATE THEN ADD_MONTHS(B.C06FECHACOR, -1) - 1 ELSE B.C06FECHACOR - 1 END
GROUP BY C.C06NOMBRE

内容的提问来源于stack exchange，提问作者Diego Solano