Question

我想删除“CASE ... WHEN ... END”语句并使用CTE或其他提示。你有更好的方法吗？还是更好的要求？

SQL：

SELECT C.COLUMN_NAME
       , DATA_TYPE
       , CHARACTER_MAXIMUM_LENGTH
       , IS_NULLABLE
       , COLUMNPROPERTY(object_id(C.TABLE_SCHEMA+'.'+C.TABLE_NAME), 
C.COLUMN_NAME, 'IsIdentity') AS IS_IDENTITY
       , CASE I.IS_PRIMARY WHEN 1 THEN 1 ELSE 0 END AS IS_PRIMARY
       , case I.IS_FOREIGN WHEN 1 THEN 1 ELSE 0 END AS IS_FOREIGN
FROM INFORMATION_SCHEMA.COLUMNS C

LEFT JOIN (
    SELECT COLUMN_NAME
        , OBJECTPROPERTY(OBJECT_ID(CONSTRAINT_SCHEMA + '.' + 
QUOTENAME(CONSTRAINT_NAME)), 'IsPrimaryKey') AS IS_PRIMARY
        , OBJECTPROPERTY(OBJECT_ID(CONSTRAINT_SCHEMA + '.' + 
QUOTENAME(CONSTRAINT_NAME)), 'IsForeignKey') AS IS_FOREIGN
    FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
    WHERE TABLE_NAME='MYTABLE'
) I ON C.COLUMN_NAME = I.COLUMN_NAME

WHERE C.TABLE_NAME='MYTABLE'

谢谢

Answer 1

您可以使用ISNULL或COALESCE将NULL值设为默认值。这消除了您的CASE声明。

SELECT C.COLUMN_NAME
       , DATA_TYPE
       , CHARACTER_MAXIMUM_LENGTH
       , IS_NULLABLE
       , COLUMNPROPERTY(object_id(C.TABLE_SCHEMA+'.'+C.TABLE_NAME), 
C.COLUMN_NAME, 'IsIdentity') AS IS_IDENTITY
       , ISNULL(I.IS_PRIMARY,0) AS IS_PRIMARY
       , ISNULL(I.IS_FOREIGN,0) AS IS_FOREIGN
FROM INFORMATION_SCHEMA.COLUMNS C

LEFT JOIN (
    SELECT COLUMN_NAME
        , OBJECTPROPERTY(OBJECT_ID(CONSTRAINT_SCHEMA + '.' + 
QUOTENAME(CONSTRAINT_NAME)), 'IsPrimaryKey') AS IS_PRIMARY
        , OBJECTPROPERTY(OBJECT_ID(CONSTRAINT_SCHEMA + '.' + 
QUOTENAME(CONSTRAINT_NAME)), 'IsForeignKey') AS IS_FOREIGN
    FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
    WHERE TABLE_NAME='MYTABLE'
) I ON C.COLUMN_NAME = I.COLUMN_NAME

Answer 2

在简单的二进制情况下，我宁愿替换

而不是case

CASE I.IS_PRIMARY WHEN 1 THEN 1 ELSE 0 END

与

IIF(I.IS_PRIMARY = 1, 1, 0)

我相信它们的工作方式与我们关注的速度相同，但IIF()更具人性化......

Answer 3

从我在这里看到的：

https://docs.microsoft.com/en-us/sql/t-sql/functions/objectproperty-transact-sql?view=sql-server-2017

事实上，这些案件毫无用处。您可以删除

case ..... end

从两行开始

SQL优化案例何时（MSSQL）

3 个答案: