Category: SQL

SQL

ANY, ALL & SOME Operators in SQL Server

ANY is a SQL operator that used to compare a scalar value with a set of single column resultset from a subquery. If any one of the value in the resultset is satifying the operator condition to the scalar value, then it return TRUE, else FALSE.

--Table Creation
create Table EmpDetails
(
	EmployeeID int,
	EmployeeName Varchar(200),
	Grade Int
)
CREATE tABLE EmpYears
(
	EmployeeID int,
	YearOfExp Int
)

--Data Population
Insert into EmpDetails Values 
(1,'Employee1',3),(2,'Employee1',4),(3,'Employee1',5),
(4,'Employee1',6),(5,'Employee1',7),(6,'Employee1',8),
(7,'Employee1',9)

Insert into EmpYears Values 
(1,3),(2,5),(3,7),(4,10),
(5,15),(6,20),(7,25)

--Get the employees with experiences more than 10 years
Select * From EmpDetails 
    where EmployeeID = ANY(Select EmployeeID From EmpYears where YearOfExp>10)

Drop Table EmpDetails, EmpYears

SOME operator is also working similar to ANY, the below returns same output as ANY.

--Get the employees with experiences more than 10 years
Select * From EmpDetails 
    where EmployeeID = SOME(Select EmployeeID From EmpYears where YearOfExp>10)

ALL operator in SQL Server returns TRUE if *all* the resultset from subquery is true to the operator condition to the scalar value.

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Errors and Exceptions, SQL, SQL Server

Exception: “Invalid parameter 1 specified for datediff.” in SQL Server

Problem Statement:

One of the view creation scripts in our deployment failed continuously with the below exception:

Invalid parameter 1 specified for datediff.
Incorrect syntax near the keyword ‘AS’.

The root cause of this error is as below.

FLOOR((DATEDIFF("W",ml.column1,ML.column2)+1)/7) AS aliasname

Solution:

FLOOR((DATEDIFF(W,ml.column1,ML.column2)+1)/7) AS aliasname

The change is that the datepart has been modified to remove the double quote.

SQL, SQL Server, T-SQL

SQL Behaviour – Assignment of value to Variable

We are going to see the SQL Behaviour while assigning value to variable, we thought of writing this post since recently we came across issues in real time during data assignment and processing.

Case 1:- First let’s see the example of direct value assignment in SQL,

declare @valueAssign nvarchar(50)='', @valueIntAssign int
set @valueAssign='YYYY'
set @valueIntAssign=1111
select @valueAssign as Fullname_DirectAssign
select @valueIntAssign as Number_DirectAssign

Output:-

Case 2:- Now we will see the Random value assignment in SQL, there are 3 rows in the table but it randomly picked the data from 3rd row during the execution.

declare @valueAssign nvarchar(50)='', @valueIntAssign int
set @valueAssign='YYYY'
set @valueIntAssign=1111
select @valueAssign as Fullname_DirectAssign
select @valueIntAssign as Number_DirectAssign

drop table if exists DataValueAssign

create table DataValueAssign(
id int,
fullname nvarchar(50),
Age int
)
insert into DataValueAssign values (1,'AAAA',19),(2,'CCCC',54),(3,'BBBB',34)
---Data Value Assigned Randomly to the Variable--
select @valueAssign=fullname,@valueIntAssign=age from DataValueAssign
select @valueAssign as Fullname_Randomly, @valueIntAssign as Age_Randomly

Output:-

Case 3:- Now let’s see how we can handle this Random value assignment behaviour by using the “Order by” and “Top” functions and assign the appropriate values to the variable and use it for data processing.

declare @valueAssign nvarchar(50)='', @valueIntAssign int
set @valueAssign='YYYY'
set @valueIntAssign=1111
select @valueAssign as Fullname_DirectAssign
select @valueIntAssign as Number_DirectAssign

drop table if exists DataValueAssign

create table DataValueAssign(
id int,
fullname nvarchar(50),
Age int
)
insert into DataValueAssign values (1,'AAAA',19),(2,'CCCC',54),(3,'BBBB',34)
---First Data Value Assigned to the Variable using order by ID--
select @valueAssign=fullname,@valueIntAssign=age from DataValueAssign order by ID desc
select @valueAssign as Fullname_FirstValue_using_Orderby,@valueIntAssign as Age_FirstValue_using_Orderby
---Top 1 Data Value Assigned to the Variable using order by AGE desc--
select top 1 @valueAssign=fullname,@valueIntAssign=age from DataValueAssign order by age desc
select @valueAssign as Fullname_Top1_Orderby_desc, @valueIntAssign as Age_Top1_Orderby_desc
---Top 1 Data Value Assigned to the Variable using order by AGE--
select top 1 @valueAssign=fullname,@valueIntAssign=age from DataValueAssign order by age
select @valueAssign as Fullname_Top1_Orderby_asc, @valueIntAssign as Age_Top1_Orderby_asc

Output:-

Be aware while assigning value to SQL variable and make sure that the expected value was set to variable, enjoy exploring SQL, Happy Learning !!!

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Linked Server, SQL

Error Message: Server is not configured for RPC in SQL Server

Recently one of my colleague reached out to me with an error message as : “Server is not configured for RPC”

This a typical issue with Linked Server. When we configure a linked server, we need to set up the right values for RPC & RPC Out . We can see these values in SSMS -> Right click on Linked Server -> Properties -> Server Options as in the below screen shot.

RPC / RPC OutRPC stands for Remote Procedure Call and allows you to run stored procedures on the Linked Server.  RPC enables Remote Procedure Calls from the specified server and RPC OUT enables Remote Procedure Calls to the specified server.

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DataTypes, SQL

Computed columns in SQL Server

What are computed columns in SQL Server

Computed columns are virtual columns that does not physically store the data in SQL Server unless it is marked as PERSISTED column. Computed columns can be defined by expression that can use other columns of the same table or static expressions.

Limitations

  1. It cannot be part of INSERT/UPDATE statement.
  2. It cannot defined as FOREIGN KEY/DEFAULT or NOT NULL constraint.

How to add a computed column while creating a table?

Create Table SampleComputedTable
(
	EmpName varchar(50),
	DOB Date,
	Age as Datediff(year,DOB,GETDATE())
)

--Today is -> '2021-07-25'; for simple explantion, the Age is calculated only year part.
Insert into SampleComputedTable Values ('Latheesh','2019-07-25')

Select * From SampleComputedTable

Drop table SampleComputedTable

How to add a computed column to an existing table? 

Alter Table SampleComputedTable Add AgeInMonths as DateDiff(month,DOB,Getdate())

Select * From SampleComputedTable

What are the best practices while creating a computed column?

There is NO way to alter computed column. You will have to drop and recreate it. 

How to find the definition of a computed column?

Select object_name(object_id) TableName, name as ColumnName, definition From sys.computed_columns 
where name='Age' and object_name(object_id) = 'SampleComputedTable'

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