Use a variable for table name [duplicate]

问题

Possible Duplicate:
how do find the number of rows in a table when the table name is in a variable?

I need to find tables in a SQL Server database (2000) that contain one value for a column.

I can use the following query to output a list of possible candidate tables containing my_column:

SELECT DISTINCT TABLE_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE COLUMN_NAME = 'my_column'

What I would like to get at, is the following pseudo query with result:

select '$TABLE_NAME', count(*) from $TABLE_NAME where my_column = '12345'

table01 1
table02 5
table03 0
table04 3

Or more generally formulated: Is it possible to make the FROM-clause variable?

回答1:

Only way it's possible is by using dynamic SQL:

declare @stmt nvarchar(max), @value nvarchar(max)

select @stmt = isnull(@stmt + ' union all ', '') + '
    select ''' + TABLE_NAME +  ''', count(*) from ' +  TABLE_NAME + ' where my_column = @value' 
from INFORMATION_SCHEMA.COLUMNS
where COLUMN_NAME = 'my_column'

select @value = '12345'

exec sp_executesql
    @stmt = @stmt,
    @params = N'@value nvarchar(max)',
    @value = @value

update:
For SQL 2000 you can use nvarchar(4000) If you have really big number of tables, you can use temporary table + cursor:

create table #Temp_Results (table_name nvarchar(128), cnt int)
declare @stmt nvarchar(4000), @value nvarchar(128)

declare t_cursor cursor local fast_forward for
    select 
        'select ''' + TABLE_NAME +  ''', count(*) from ' +  TABLE_NAME + ' where id = @value'
    from INFORMATION_SCHEMA.COLUMNS
    where COLUMN_NAME = 'name'

select @value = 1

open t_cursor
fetch t_cursor into @stmt
while @@fetch_status = 0
begin
    insert into #Temp_Results
    exec sp_executesql
        @stmt = @stmt,
        @params = N'@value nvarchar(128)',
        @value = @value

    fetch t_cursor into @stmt
end

close t_cursor
deallocate t_cursor

select * from #Temp_Results

回答2:

You can use the sp_MSforeachtable undocumented stored procedure to make the FROM clause variable.Here is an article that shows how to use it: sp_msForEachTable examples

回答3:

If I understand the question, you want a list of tables containing a given column name and a record count from each table, yes? If so

select o.name as "Table Name", i.rowcnt as "Rows"
from sysobjects o
inner join sysindexes i on o.id = i.id
where i.indid in (0,1)
and o.id in
    (select distinct id from syscolumns where name = 'My_Column')
order by o.name

Requires that you have ability to query system tables.

来源：https://stackoverflow.com/questions/13630347/use-a-variable-for-table-name

标签

sql

sql-server

tsql

variables

sql-server-2000