Question

我试图在NamedParameterJdbcTemplate中使用查询，为Postgresql编写if条件的查询。

我将2个参数传递给query，store和tot_store。我尝试了以下查询，但它不起作用。有什么建议吗？

IF (:store=1)
BEGIN 
    SELECT * FROM store_pricing WHERE store = :store and tot_store = :tot_store ORDER BY store asc;
END
ELSE IF (:store = 2)
BEGIN
    SELECT * FROM store_pricing WHERE store = :store and tot_store = :tot_store ORDER BY store asc;
END
ELSE
BEGIN
    SELECT * FROM store_pricing WHERE store = :store and tot_store = :tot_store ORDER BY store desc;
END

错误说

syntax error at or near "IF"

提前谢谢

Answer 1

PostgreSQL doesn't accept IF as a top level statement. It's not SQL-standard either.

Use CASE ... WHEN ...

IF is permitted in PL/PgSQL code blocks, though; see DO and CREATE FUNCTION.

In this case I'd write a single SQL statement and

ORDER BY
  CASE WHEN store IN (1,2) THEN -store
  ELSE store
  END DESC

(untested)

Answer 2

如果您使用的是Mysql，则代码中的IF语句不正确。正确的IF语法：

IF search_condition THEN statement_list
    [ELSEIF search_condition THEN statement_list] ...
    [ELSE statement_list]
END IF

你需要摆脱括号，然后把它放在条件之后。

例如，您可以编写这样的存储过程：

DELIMITER //

CREATE FUNCTION SimpleCompare(n INT, m INT)
  RETURNS VARCHAR(20)

  BEGIN
    DECLARE s VARCHAR(20);

    IF n > m THEN SET s = '>';
    ELSEIF n = m THEN SET s = '=';
    ELSE SET s = '<';
    END IF;

    SET s = CONCAT(n, ' ', s, ' ', m);

    RETURN s;
  END //

DELIMITER ;

注意，在Mysql中还有另一个IF。它是一个可以在select语句中使用的函数。

官方文档：https://dev.mysql.com/doc/refman/5.7/en/if.html

IF ... <sql query =“”> .... ELSE IF .... <sql query =“”> ... Else

2 个答案: