Find last statistics updated date detail ?–Maintenance TIP #59

 

Problem:- One of the pain point in any SQL engineer  is “Performance”. There are various reasons due to which your SQL Server database is slow.

One of the possible reason is your maintenance.   You don’t know when statistics last updated and take further step if those are not updated

Solution:-

Here we have simple query to find when the statistics was last updated for a table.

SELECT o.name,
       i.name AS [Index Name], 
       STATS_DATE(i.[object_id], i.index_id) AS [Statistics Date],
       s.auto_created,
       s.no_recompute,
       s.user_created
FROM sys.objects AS o WITH (NOLOCK)
INNER JOIN sys.indexes AS i WITH (NOLOCK) ON o.[object_id] = i.[object_id]
INNER JOIN sys.stats AS s WITH (NOLOCK)   ON i.[object_id] = s.[object_id]
                      AND i.index_id = s.stats_id
WHERE o.[type] = 'U'
ORDER BY STATS_DATE(i.[object_id], i.index_id) ASC;  

When you run it you will find last statistics update date if it is too old it means you have to run the maintenance for those tables.

see below screenshot which I run on my machines adventureworks2012 database.

I am sure you will analyze your database tables stats and run maintenance accordingly.

I hope this tip may help you some where.

Enjoy !!!

Rj!!

Merge Statement one of the way to synch destination from source table TIP# 58

 

Problem:-  Suppose you have a source table and one destination table and you want to synch destination table from source table. means if record is already exists then you need to update and the record with latest value and insert the record if record is not exists.

Solution:-  Although there are various ways exist but here we are using a new feature came in SQL Server 2008 which is MEGE statement.

Suppose we have a  tblStudentSource table and one tblStudentDestination table

both have equal columns as shown in below figure.

both have studentId, Firstname, LastName & course column

 

if you see above figure you will find that destination table there are 2 rows while in tblstudentSource table we have 3 rows.

Now if you see in tblStudentDestination LastName of StudentID  2 is spelled wrong.

So what we have to do here. We have to Insert a new row from tblStudentSource and update existing row.

To achieve this we will use merge statement as shown in figure

Now if you see above snap  we write basic merged statement which check condition of tblSource and destination table and if condition is matched then we wrote update statement if not matched then we wrote insert statement.

MERGE tblStudentDestination AS Destination
USING tblStudentSource  AS Source
ON Source.StudentId = Destination.StudentId
WHEN MATCHED THEN
UPDATE
SET Destination.FirstName = Source.FirstName,
    Destination.LastName = Source.LastName,
    Destination.Course = Source.Course
WHEN NOT MATCHED THEN
INSERT (FirstName,LastName,Course)
VALUES (Source.FirstName,source.LastName,Source.Course);
    

Now we run above statement we got the desire result and our source and destination table is in synched.

I hope this post may help and give you a general Idea of merge statement.

Thanks!!!

RJ!!!

A hidden feature sp_MSforeachtable–run on entire tables of a Database TIP# 51

Problem:-

Sometimes it happened that you need to run a single statement on entire tables which exists in database.  so most of the time we think of cursor which run for each sys.objects (table)  and we execute the dynamic statement by replacing table name.

Solution:

Although the solution we are thinking is correct there is no issue at all but SQL SERVER made our life more each by providing “sp_MSForEachTable”  which is a hidden stored procedure.

By the name it is clear that it will run on each table.

Lets understand this by an example. Suppose you want to  row count of each table then you can write following statement.

DECLARE @tblRowCount AS TABLE (Counts  INT,
                               TableName VARCHAR(100))

INSERT INTO @tblRowCount (Counts,TableName)
EXEC sp_MSforeachtable
@command1='SELECT COUNT(1) As counts,''?'' as tableName FROM ?'

SELECT * FROM @TblRowCount ORDER BY Counts desc

Now when we run it we will get row count of each table as shown in below snap

 

A part from it you can use this hidden feature in maintenance also like running re indexing, re organizing entire table index etc.

I hope this may help you some where.

Enjoy!!!

RJ!!