While Loop to Iterate through Databases

Question

I was wondering if someone could help me with creating a while loop to iterate through several databases to obtain data from one table from two columns. this is was I have done so far. nothing works because i do not know how to make the select statement work through each database with regards to the table that I am querying from each database (dbo.tbldoc)

DECLARE @Loop int
DECLARE @DBName varchar(300)
DECLARE @SQL varchar(max)
DECLARE @tableName VARCHAR(255)

SET @Loop = 1
SET @DBName = ''

   WHILE @Loop = 1
BEGIN

   SELECT [name] FROM sys.databases 
   WHERE [name] like 'z%' and create_date between '2010-10-17' and '2011-01-15'
   ORDER BY [name]

      SET @Loop = @@ROWCOUNT

   IF @Loop = 0
      BREAK

   SET @SQL = ('USE ['+ @DBNAME +']')
      IF EXISTS(SELECT [name] FROM sys.tables WHERE name != 'dbo.tbldoc' )
                  BEGIN
               SELECT SUM(PGCOUNT), CREATED FROM **dbo.tbldoc**
            END
            ELSE
            --BEGIN
               PRINT 'ErrorLog'
            END 

Answer 1

I would consider sp_MSForEachDB which is a lot easier...

Edit:

EXEC sp_MSForEachDB 'USE [?]; IF DB_NAME() LIKE ''Z%%''
BEGIN


END
'

Answer 2

CREATE TABLE #T
(dbname sysname NOT NULL PRIMARY KEY,
SumPGCOUNT INT,
CREATED DATETIME)

DECLARE @Script NVARCHAR(MAX) = ''

SELECT @Script = @Script + '

USE ' + QUOTENAME(name) + '
IF EXISTS(SELECT * FROM sys.tables WHERE OBJECT_ID=OBJECT_ID(''dbo.tbldoc''))
  INSERT INTO #T
  SELECT db_name() AS dbname, SUM(PGCOUNT) AS SumPGCOUNT, CREATED 
  FROM dbo.tbldoc
  GROUP BY CREATED;  
  '
FROM sys.databases 
WHERE state=0 AND user_access=0 and has_dbaccess(name) = 1
 AND [name] like 'z%' and create_date between '2010-10-17' and '2011-01-15'
ORDER BY [name]

IF (@@ROWCOUNT > 0)
 BEGIN
 --PRINT @Script
 EXEC (@Script)
 SELECT * FROM #T
 END

 DROP TABLE #T