从名称作为变量传递的表中进行选择 [英] Selecting from a table where the name is passed as a variable

问题描述

我正在尝试编写一个简单的存储过程，它采用三个参数数据库名称一"、数据库名称二"和表名称".然后sql会对每个数据库中定义的表进行行计数并存储.

I am trying to write a simple stored proc which takes three arguments 'database name one', 'database name two' and 'table name'. The sql will then perform a row count for the defined table in each database and store it.

零碎地工作 我遇到了你做不到的第一个问题

Working on it piecemeal I have hit the first problem in that you can't do

select * from @tablename

我知道您可以通过 exec 命令使用动态 sql，但这并不理想，因为我无法返回值.

I know you can use dynamic sql with the exec command but this is not ideal as I can't return values.

下面的例子看起来应该可以，但没有.

The following example looks like it should work but doesn't.

declare @tablename as nvarchar(500)
declare @sqlstring as nvarchar(500)
declare @parmdefinition as nvarchar(500)
declare @numrows as bigint

set @tablename = N'dummy_customer'

set @parmdefinition = N'@tablenameIN nvarchar(500), @numrowsOUT as bigint OUTPUT'

select @sqlstring = 'select @numrowsOUT = count(*) from @tablenameIN'

select @sqlstring

exec sp_executesql @sqlstring, @parmdefinition, @tablenameIN = @tablename, @numrowsOUT = @numrows OUTPUT

select @numrows

给出的错误信息是

Msg 1087, Level 16, State 1, Line 1
Must declare the table variable "@tablenameIN".

目前使用的是 SQL Server 2008 SP2.

Currently using SQL Server 2008 SP2.

我们这样做是因为我们正在进行迁移，而客户想要一份报告，该报告显示源数据库和目标数据库中每个表的行数.由于有许多表能够使用 sp_MSForEachTable 来调用存储过程似乎是理想的.

We're doing this because we are doing a migration and the customer wants a report which shows the row count for each table in the source and destination database. As there are many tables being able to use sp_MSForEachTable to call the stored proc seems ideal.

供将来参考的最终解决方案是

The final solution for future reference is

declare @tablename as nvarchar(500)
declare @sqlstring as nvarchar(500)
declare @parmdefinition as nvarchar(500)
declare @numrows as bigint

set @tablename = N'dummy_customers'

set @parmdefinition = N'@tablename nvarchar(500), @numrowsOUT as bigint OUTPUT'

select @sqlstring = 'select @numrowsOUT = count(*) from ' + quotename(@tablename)

exec sp_executesql @sqlstring, @parmdefinition, @tablename = @tablename, @numrowsOUT = @numrows OUTPUT

select @numrows

推荐答案

你必须使用动态 sql，并将表名连接到 SQL 字符串中，然后通过 sp_executsql 执行:

You'd have to use dynamic sql, and concatenate the table name into the SQL string to then execute via sp_executsql:

select @sqlstring = 'select @numrowsOUT = count(*) from ' + QUOTENAME(@tablename)
EXECUTE sp_executesql ....

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