Tempdb Sizing

Many DBA’s Prefer to set 100-200 GB size for  database tempdb,  out of this space 90 % for data file(.mdf) and 10% for Log file(.ldf), this sizing help to prevent uncontrolled size growth & reduce contention.

MAX Value From Multiple Columns

CREATE TABLE #MAXCOLUMNVALUES
(ID INT IDENTITY(1,1)
,INFYSalary INT, WIPROSalary INT, SYNESalary INT, TCSSalary INT
)


INSERT INTO #MAXCOLUMNVALUES(InfySalary,WiproSalary,SyneSalary,TCSSalary) VALUES
(10000,20000,33000,25000),
(20000,55000,35000,45000),
(40000,24000,66000,50000),
(50000,51000,53000,77000),
(44000,32000,38000,30000)

SELECT * FROM #MAXCOLUMNVALUES
-- Select Max value from Multiple columns as column name MAXSalary

SELECT
*, (SELECT MAX(MaxSalary) FROM (VALUES (InfySalary),(WiproSalary),(SyneSalary),(TCSSalary)) AS Salary(MaxSalary)) AS MAXSalary
 FROM #MAXCOLUMNVALUES

QUERY TO GET REVERSE DUPLICATE

Create Table with Reverse Duplicate Data

CREATE TABLE GETREVERSEDUPLICATE
(COL1 VARCHAR(10),COL2 VARCHAR(10) ,COL3 INT)

INSERT INTO GETREVERSEDUPLICATE
SELECT 'A','B',10
UNION
SELECT 'C','D',20
UNION
SELECT 'B','A',10
UNION
SELECT 'D','C',20



SELECT * FROM GETREVERSEDUPLICATE
OUTPUT:
COL1 COL2 COL3
A B 10
B A 10
C D 20
D C 20

GET REVERSE DUPLICATE WITH EXPECTED OUTPUT
EXPECTED RESULT:
COL1 COL2 COL3
B A 10
D C 20



Query:
SELECT * FROM GETREVERSEDUPLICATE T
 WHERE Col1 > Col2
       AND EXISTS (
                   SELECT *
                     FROM GETREVERSEDUPLICATE  AS T1
                    WHERE T1.Col1 = T.Col2
                          AND T1.Col2 = T.Col1
                  );

OUTPUT:
COL1 COL2 COL3
B A 10
D C 20


Please try in Test environment only.

SQL Server Logins vs Database Users

SQL Server Login is used to Access SQL Server means for Authentication but Database users

are specific to a database to perform database operation based on database role membership and the permission under the tab securables means for Authorization.

After creation of login named SQLLogin as per above figure it will create the user in database Capital with user name SQLLogin with default schema [dbo]

SQL script for SQL Login as per above figure.

CREATE LOGIN [SQLLogin] WITH PASSWORD='random encrypted password', DEFAULT_DATABASE=[master],

DEFAULT_LANGUAGE=[us_english], CHECK_EXPIRATION=OFF, CHECK_POLICY=OFF

GO

We can see in above image SQLLogin is marked as user in database Capital thus it will

Create database user in database Capital using below SQL Script.

CREATE USER [SQLLogin] FOR LOGIN [SQLLogin] WITH DEFAULT_SCHEMA=[dbo]

Once SQL server login and respective database user is created we cannot delete the SQL Server logins if said SQL Login is used to access the SQL Server or database user is still associated with said SQL Login.

Database Role members.

We can create Database user with different types, shown in below figure

As per above image from securables tab we can give required permissions/authorization to database users for database objects (tables/view/sp’s etc.)

SQL Script to create user without SQL Login:

CREATE USER [sqlwologin] WITHOUT LOGIN WITH DEFAULT_SCHEMA=[dbo]

ISNULL vs COALESCE vs NULLIF

TableDiff.exe Utility

Tablediff.exe  command line utility

SQL server has command line utility tablediff.exe, using this we can easily compare source and destination tables. This is generally used in replication topology.

We can use it from command prompt or by using batch file.

We can perform following

1.       Row by row comparison

2.       Row count or schema comparison

3.       Column level comparison

4.       Generate t-SQL script to have data in sync with source and destination

5.       Log comparison output into file or in destination database table.

Utility required list of parameters but some rudimentary parameters are below

1.       -sourceserver 

2.       -sourcedatabase 

3.       -sourcetable

4.       -destinationserver 

5.       -destinationdatabase 

6.       -destinationtable 

Let us create tables for source and destination comparison

Source Table:

CREATE TABLE TableDiffSource

(TDID INT PRIMARY KEY, TDDescription VARCHAR(100))

INSERT INTO TableDiffSource

SELECT 1,'A'

UNION

SELECT 2,'B'

UNION

Select 4,'D'

Destination Table:

CREATE TABLE TableDiffDestination

(TDID INT PRIMARY KEY, TDDescription VARCHAR(100))

INSERT INTO TableDiffDestination

SELECT 1,'A'

UNION

SELECT 2,'B'

UNION

SELECT 3,'C'

Open the command prompt and execute below command by changing your Server & Database names.

In command I have used. 

SourceServcer: SQLSourceServerName & SourceDatabase= Capital

DestinationServer= SQLDestinationServerName & DestinationDatabase=  Capital

C:\Program Files\Microsoft SQL Server\120\COM>tablediff.exe -sourceserver SQLSourceServerName -sourcedatabase Capital -sourcetable tablediffsource -destinationserver

 SQLDestinationServerName -destinationdatabase Capital -destinationtable tablediffdestinat

ion -et tableDiffoutput

It will look like below after execution of tablediff.exe utility, in image i have hidden soruceserver & destinationServer names, please change them as per your SQL Server details

Let us check the difference, in output table

select * FROM tablediffoutput

output

TDID	MSdifftool_ErrorCode	MSdifftool_ErrorDescription	my Comments
3	1	Dest. Only	Present in Destination but not in source table
4	2	Src. Only	Present in source but not in destination table

Note: in above output, column myComments I have added for more clarification marked in color olive green.

for more details, please visit below link .

https://msdn.microsoft.com/en-IN/library/ms162843.aspx