IIF 函数从 SQL 到 HSQLDB

Question

我在 MS Access 中有以下 SQL 语句 -

WITH 
    qryAwayMatches AS (SELECT MATCHTEAM.FOOTBALLMATCHID, MATCHTEAM.TEAMID, MATCHTEAM.GAMETYPE, MATCHPROTOCOL.MATCHTEAMID, MATCHPROTOCOL.GOALNUMBER, 
    MATCHPROTOCOL.YELLOWCARDNUMBER, MATCHPROTOCOL.REDCARDNUMBER FROM MATCHTEAM LEFT JOIN MATCHPROTOCOL ON MATCHTEAM.ID = MATCHPROTOCOL.MATCHTEAMID WHERE (((MATCHTEAM.GAMETYPE)='Away'))),
    qryHomeMatches AS (SELECT MATCHTEAM.FOOTBALLMATCHID, MATCHTEAM.TEAMID, MATCHTEAM.GAMETYPE, MATCHPROTOCOL.MATCHTEAMID, MATCHPROTOCOL.GOALNUMBER, 
    MATCHPROTOCOL.YELLOWCARDNUMBER, MATCHPROTOCOL.REDCARDNUMBER FROM MATCHTEAM LEFT JOIN MATCHPROTOCOL ON MATCHTEAM.ID = MATCHPROTOCOL.MATCHTEAMID WHERE (((MATCHTEAM.GAMETYPE)='Home'))),
    qryMatchResult AS (SELECT qryHomeMatches.FootballMatchID, qryHomeMatches.TeamID AS HomeTeamID, 
    qryAwayMatches.TeamID AS AwayTeamID, 
    qryHomeMatches.GoalNumber>qryAwayMatches.GoalNumber AS HomeTeamWin, 
    qryHomeMatches.GoalNumber=qryAwayMatches.GoalNumber AS NoWin, 
    qryHomeMatches.GoalNumber<qryAwayMatches.GoalNumber AS AwayTeamWin 
    FROM qryHomeMatches INNER JOIN qryAwayMatches ON qryHomeMatches.FootballMatchID = qryAwayMatches.FootballMatchID)
    SELECT Round.RoundNumber, Team.Name, **IIf([HomeTeamWin],3,IIf([NoWin],1,0)) AS Points** 
    FROM Round 
    INNER JOIN (Team INNER JOIN (RoundDetail INNER JOIN qryMatchResult ON RoundDetail.FootballMatchID = qryMatchResult.FootballMatchID) ON Team.ID = qryMatchResult.HomeTeamID) ON Round.ID = RoundDetail.RoundID;

当我尝试使用 HSQLDB 在 Java 中按下按钮时执行此语句时，出现以下错误：

java.sql.SQLSyntaxErrorException: user lacks privilege or object not found: IIF

我该如何解决这个问题？

Answer 1

从文档看来，HSQLDB 不支持 IIF 函数，我在函数列表中找不到它:
http://hsqldb.org/doc/2.0/guide/builtinfunctions-chapt.html#bfc_general_functions

不过好消息是：HSQLDB支持case表达式：
http://hsqldb.org/doc/2.0/guide/dataaccess-chapt.html#dac_query_expression

CASE

case specification

::= |

::= CASE ... [ ] END

::= CASE ... [ ] END

::= WHEN THEN

::= WHEN THEN

::= ELSE

::= |

::= [ { }... ]

::= | | | | | | | | | | | |

::= | NULL

::=

case 表达式由 ANSII SQL 标准定义，大多数数据库都支持，而 IIF 函数是专有的和非标准的。

你可以改写：

iif ( condition, value_if_true, value_if_false )

以这种方式使用 case 表达式：

CASE WHEN condition THEN value_if_true ELSE value_if_false END

例如：

SELECT CASE WHEN col1>1 THEN 20 ELSE 50 END
FROM ....

而不是

SELECT iif(col1>1,20,50)
FROM ...

IIF 函数从 SQL 到 HSQLDB

IIF Function from SQL to HSQLDB

java

database

subquery

hsqldb

iif