DB2存储过程IF语句

Question

我目前正在试验存储过程，我尝试实现一个简单的IF / ELSE语句。我正在使用DB2，如果procedure参数为null，并且如果参数不为null，则我尝试选择所有记录，查询数据库。

我的存储过程代码如下：

    DROP PROCEDURE LWILSON.IFQUERY@
CREATE PROCEDURE LWILSON.IFQUERY
(
    IN p_type VARCHAR(15)
)

DYNAMIC RESULT SETS 1
LANGUAGE SQL
BEGIN
DECLARE c_result CURSOR WITH RETURN FOR
IF p_type IS NULL
THEN
SELECT * FROM LWILSON."ANIMALS";
OPEN c_result;
ELSE 
SELECT ID,TYPE,NAME,WEIGHT, AGE FROM LWILSON."ANIMALS" AS ANIMALRESULTS WHERE ANIMALRESULTS.type = p_type;
OPEN c_result;
END IF;
END@

（我使用@符号作为命令分隔符）。 我在尝试执行该过程时收到的错误消息如下...

感谢任何帮助。感谢。

Answer 1

您可以通过准备要执行的语句来实现。在这种情况下，您不需要两个游标：

CREATE OR REPLACE PROCEDURE LWILSON.IFQUERY (
    IN p_type VARCHAR(15)
)
  DYNAMIC RESULT SETS 1
  LANGUAGE SQL
 BEGIN
  DECLARE STMT VARCHAR(120);
  DECLARE c_result CURSOR
    WITH RETURN FOR RES_SET;

  IF (p_type IS NULL) THEN
   SET STMT = "SELECT * FROM LWILSON.ANIMALS";
  ELSE 
   SET STMT = "SELECT ID, TYPE, NAME, WEIGHT, AGE "
     || "FROM LWILSON.ANIMALS AS ANIMALRESULTS "
     || "WHERE ANIMALRESULTS.type = " || p_type;
  END IF;
  PREPARE RES_SET FROM STMT
  OPEN c_result;
 END@

Answer 2

我找到的最佳选择是为每个条件创建一个光标并打开你需要的光标。

DECLARE cursor1 CURSOR
    WITH RETURN FOR SELECT * FROM LWILSON.ANIMALS;
DECLARE cursor2 CURSOR
    WITH RETURN FOR SELECT * FROM LWILSON.ANIMALS AS ANIMALRESULTS
    WHERE ANIMALRESULTS.type = p_type;

IF (p_type IS NULL) THEN
    OPEN cursor1;
ELSE 
    OPEN cursor2;     
END IF;