In SQL Server, a procedure is a stored program that you can pass parameters into. It does not return a value like a function does. However, it can return a success/failure status to the procedure that called it.
Authors table in the Library Database
CREATE PROCEDURE GetName ( @input_id INT = NULL, --Input parameter, id of the person, NULL default @name VARCHAR(128) = NULL --Input parameter, name of the person, NULL default ) AS BEGIN SELECT Name + ' is from ' + Country FROM Authors WHERE Id = @input_id OR Name = @name END GO
You can execute a procedure with a few different syntaxes. First, you can use
EXECUTE GetName @id = 1 EXEC Getname @name = 'Ernest Hemingway'
Additionally, you can omit the EXEC command. Also, you don't have to specify what parameter you are passing in, as you pass in all parameters.
GetName NULL, 'Ernest Hemingway'
When you want to specify the input parameters in a different order than how they are declared in the procedure you can specify the parameter name and assign values. For example
CREATE PROCEDURE dbo.sProcTemp ( @Param1 INT, @Param2 INT ) AS BEGIN SELECT Param1 = @Param1, Param2 = @Param2 END
the normal order to execute this procedure is to specify the value for @Param1 first and then @Param2 second. So it will look something like this
EXEC dbo.sProcTemp @Param1 = 0,@Param2=1
But it's also possible that you can use the following
EXEC dbo.sProcTemp @Param2 = 0,@Param1=1
in this, you are specifying the value for @param2 first and @Param1 second. Which means you do not have to keep the same order as it is declared in the procedure but you can have any order as you wish. but you will need to specify to which parameter you are setting the value
Access stored procedure from any database
And also you can create a procedure with a prefix
sp_ these procuedres, like all system stored procedures, can be executed without specifying the database because of the default behavior of SQL Server. When you execute a stored procedure that starts with "sp_", SQL Server looks for the procedure in the master database first. If the procedure is not found in master, it looks in the active database. If you have a stored procedure that you want to access from all your databases, create it in master and use a name that includes the "sp_" prefix.
Use Master CREATE PROCEDURE sp_GetName ( @input_id INT = NULL, --Input parameter, id of the person, NULL default @name VARCHAR(128) = NULL --Input parameter, name of the person, NULL default ) AS BEGIN SELECT Name + ' is from ' + Country FROM Authors WHERE Id = @input_id OR Name = @name END GO
Stored procedures can return values using the
OUTPUT keyword in its parameter list.
CREATE PROCEDURE SprocWithOutParams ( @InParam VARCHAR(30), @OutParam VARCHAR(30) OUTPUT ) AS BEGIN SELECT @OutParam = @InParam + ' must come out' RETURN END GO
DECLARE @OutParam VARCHAR(30) EXECUTE SprocWithOutParams 'what goes in', @OutParam OUTPUT PRINT @OutParam
CREATE PROCEDURE SprocWithOutParams2 ( @InParam VARCHAR(30), @OutParam VARCHAR(30) OUTPUT, @OutParam2 VARCHAR(30) OUTPUT ) AS BEGIN SELECT @OutParam = @InParam +' must come out' SELECT @OutParam2 = @InParam +' must come out' RETURN END GO
DECLARE @OutParam VARCHAR(30) DECLARE @OutParam2 VARCHAR(30) EXECUTE SprocWithOutParams2 'what goes in', @OutParam OUTPUT, @OutParam2 OUTPUT PRINT @OutParam PRINT @OutParam2
Create example table
CREATE TABLE Employee ( Id INT, EmpName VARCHAR(25), EmpGender VARCHAR(6), EmpDeptId INT )
Creates stored procedure that checks whether the values passed in stored procedure are not null or non empty and perform insert operation in Employee table.
CREATE PROCEDURE spSetEmployeeDetails ( @ID int, @Name VARCHAR(25), @Gender VARCHAR(6), @DeptId INT ) AS BEGIN IF ( (@ID IS NOT NULL AND LEN(@ID) !=0) AND (@Name IS NOT NULL AND LEN(@Name) !=0) AND (@Gender IS NOT NULL AND LEN(@Gender) !=0) AND (@DeptId IS NOT NULL AND LEN(@DeptId) !=0) ) BEGIN INSERT INTO Employee ( Id, EmpName, EmpGender, EmpDeptId ) VALUES ( @ID, @Name, @Gender, @DeptId ) END ELSE PRINT 'Incorrect Parameters' END GO
Execute the stored procedure
DECLARE @ID INT, @Name VARCHAR(25), @Gender VARCHAR(6), @DeptId INT EXECUTE spSetEmployeeDetails @ID = 1, @Name = 'Subin Nepal', @Gender = 'Male', @DeptId = 182666
Dynamic SQL enables us to generate and run SQL statements at run time. Dynamic SQL is needed when our SQL statements contains identifier that may change at different compile times.
Simple Example of dynamic SQL:
CREATE PROC sp_dynamicSQL @table_name NVARCHAR(20), @col_name NVARCHAR(20), @col_value NVARCHAR(20) AS BEGIN DECLARE @Query NVARCHAR(max) SET @Query = 'SELECT * FROM ' + @table_name SET @Query = @Query + ' WHERE ' + @col_name + ' = ' + ''''[email protected]_value+'''' EXEC (@Query) END
In the above sql query, we can see that we can use above query by defining values in
@table_name, @col_name, and @col_value at run time. The query is generated at runtime and executed. This is technique in which we can create whole scripts as string in a variable and execute it. We can create more complex queries using dynamic SQL and concatenation concept. This concept is very powerful when you want to create a script that can be used under several conditions.
Executing stored procedure
DECLARE @table_name NVARCHAR(20) = 'ITCompanyInNepal', @col_name NVARCHAR(20) = 'Headquarter', @col_value NVARCHAR(20) = 'USA' EXEC sp_dynamicSQL @table_name, @col_name, @col_value
Table I have used
First lets get some data into a temp table named
#systables and ad a incrementing row number so we can query one record at a time
select o.name, row_number() over (order by o.name) as rn into #systables from sys.objects as o where o.type = 'S'
Next we declare some variables to control the looping and store the table name in this example
declare @rn int = 1, @maxRn int = ( select max(rn) from #systables as s ) declare @tablename sys name
Now we can loop using a simple while. We increment
@rn in the
select statement but this could also have been a separate statement for ex
set @rn = @rn + 1 it will depend on your requirements. We also use the value of
@rn before it's incremented to select a single record from
#systables. Lastly we print the table name.
while @rn <= @maxRn begin select @tablename = name, @rn = @rn + 1 from #systables as s where s.rn = @rn print @tablename end
CREATE PROCEDURE SprocWithSimpleLoop ( @SayThis VARCHAR(30), @ThisManyTimes INT ) AS BEGIN WHILE @ThisManyTimes > 0 BEGIN PRINT @SayThis; SET @ThisManyTimes = @ThisManyTimes - 1; END RETURN; END GO