How to disable constraints of a table ? TIP #74

 

You are reading this post just because of two reason

1) You are curious whether it is possible or not and why we require ?

2) You need to disable constraints 

So , let me share here that you can disable constraints at anytime of a table.

Sometime it is possible when you are doing bulk insert or you need to insert values in column and for this you need to disable constraints.

You can disable all the constraints of a table using following command

ALTER TABLE TABLENAME NOCHECK CONSTRAINT ALL ;

If you want to disable a specific constraint of a table then you can use following syntax

ALTER TABLE TABLENAME NOCHECK CONSTRAINT_NAME

For example suppose you want to disable all the constraints of  student table then you can write following syntax

ALTER TABLE dbo.Students NOCHECK ALL;

Below is very live example in Indian scenario

Suppose you added a check marks in last class more than 45% then only add student now due to some out side pressure you want to give admission to a student who has 40% percent then you need to disable percentage check.

ALTER TABLE dbo.Student NOCHECK chk_Student_Percentage_40

I hope this might help you somewhere.

Thanks

Rj!!!

How to copy table structure only from a SQL Query ? Tip #69

 

Recently , one of my friends shared that some interviewer asked him a question “How to copy table structure only from a  SQL Query?”

So,

Below is simplest query to copy structure only of a table into another table.

SELECT *
Into #tmpStudentStructure
FROM tblStudentSource
WHERE 1= 0

in the above query we want to copy structure of tblStudentSource.

see below snap which help you to understand it more

I hope this might help you if some asked you this question.

Thanks & Enjoy!!!

RJ!!!

How easy it is to check which statements consuming most of the CPU & RAM–TIP #68

 

Problem:-  One of the most important question comes in our mind what is the cause of slow  SQL SERVER.

We always struggle with following questions

Which is highly CPU consuming query ?

Which is highly RAM consuming query ?

Who is blocking the transaction ?

and many more other performance dragging questions.

Believe me if you know who is culprit of making your system slow, you will win half battle.

Solution:-  SQL Server provided an easy way to clear your all doubts related to above questions. This easy way is “STANDARD REPORTS”.

You can access Standard Reports option by right clicking the SQL SERVER instance. These Standard reports contains not only performance related reports but other useful reports also.

If you see below image you will find there are many other reports option available.

Now, suppose I am interested to know which query consuming high CPU , to achieve this I clicked on   Performance Query – TOP Queries by Average CPU time or Performance query – Top queries  by total CPU time.

When I clicked on any of this option ,I got a report.

This report contained a bar graph & query detail in tabular format which contains query & CPU consuming time as shown below.

in similar way we can get answer of our other performance related query also.

I hope this may help you somewhere.

Thanks & Best Regards,

RJ!!

Best Practices in database design (SQL Server)

Hello friends,
Designing database is one of the most interesting works but on the same time it should be proper because it is base of any business application. We should follow Microsoft best practices while designing the database. Here I am with a simple database design (Address book) concept. I will try to put my best to use Microsoft best practices while designing database. I know you are thinking Address book is so much easy to design, so my answer is yes you are right you can design database easily but using Microsoft best practices it bit more important and I am trying for those best practices.
So first best practice is
1)Define proper data type :-
Most of the time we design database but we ignore proper database but it should not because when you talking for very large scale database application (VLSDB) then wrong data type will give you space problem. According to best practices choose smallest data type first (if it fit in your requirement).We understand this by an example suppose you designed a table with name “seed Data” in which column with name lngId having data type float and float consume 8 bytes and if the seed data cannot exceed more than 10 rows then we should use Tinyint data type instead of float data type because tinyint consume only 1 byte.
2)Define proper Primary & Foreign key:-
According to best practices we should make database normalized and for normalized database we should create proper Primary & Foreign keys. By creating proper primary & foreign keys we get two advantage 1) data anomalies chances reduce we get fast response as well after defining primary key (because cluster index created on primary key)
3)Define proper constraints :-
Microsoft best practices also suggest defining proper constraints for column like not null, unique key constraint on columns so that data anomalies will reduce and we get proper data.
4)Define partition :-
If your database is going to be very large then define proper partition both horizontally & vertically.
5)Normalization: - Database should be proper normalized.
In our Address Book database example we have categorized the data table in 3 categories

1)Lookup table having prefix “lku”
The lookup table is mainly for seed value or we can say this table contains all the data which just act like pre pop data. We have following tables for our Address book
lkuCountryMaster,lkuStateMaster,lkuCityMaster,lkuPhoneType,lkuAddressType,lkuPrefixMaster,lkuURLType,lkuDesignationType,lkuRelationShipType

2)Link table having prefix “lnk”
By the name it is clear that its main purpose is making relation between main data record and other data. We have used following tables lnkPhoneToPerson,lnkAddressToPerson,lnkAddressToCompany,lnkURLToPerson,lnkPersonToCompany,lnkPersonRelations,lnkPhoneToCompany

3)Main table which start with prefix “tbl”
The main table indicates by “tbl” in our Address book database we have used following tables tblPerson, tblAddresses, tblPhotos and tblCompany.


In the entire lookup table we have preferred tiny int & Small int data type because we know the value in look up table could not go beyond the tiny int & small int max limit.
In similar way we have applied all the not null constraint to require field provide proper data type.
Please see fig below.

For more detail you can download script for Address book.

Thanks & Esteemed Regards
Rajat Jaiswal