Sometimes you may want to run a query against each database Suppose you want to find all dabase names where particular table exists. You can use undocumented procedure

 
EXEC sp_msforeachdb 'SELECT table_catalog FROM ?.INFORMATION_SCHEMA.TABLES where table_name=''your_table'''

Because they are undocmented, you cant always rely on them. Alternatively you can use the following methods 1 WHILE LOOP

 
declare @dbname varchar(100), @database_id int,@table_name varchar(100)
select @dbname='', @database_id=1,@table_name='your_table' 
while exists(Select * from sys.databases where database_id>@database_id)
Begin
        select @dbname=name,@database_id=database_id from sys.databases where database_id=@database_id 
        EXEC('SELECT * FROM '+@dbname+'.INFORMATION_SCHEMA.TABLES where table_name='''+@table_name+'''') 
        select @database_id=min(database_id) from sys.databases where database_id>@database_id 
End

2 Concatenated SQL

 
declare @sql varchar(max), @table_name varchar(100)
select @sql='', @table_name='your_table'
select  @sql=@sql+ 'SELECT table_catalog FROM '+name+'.INFORMATION_SCHEMA.TABLES where table_name='''+@table_name+'''' from sys.databases
exec(@sql)