How to write dynamic insert statement in sql server? - sql

Question

I have a Student table and Department table.
Student Table contains Three columns
StudentId | DeptId | StudentName
Department Table contains
DeptId | DeptName
It may be the case that DeptTable sometimes doesnot exists. That is I am deploying script with two scenarios sometimes with department and sometimes without. In the case without department , departmentId will not be there in student table
So when Department table exists I have to insert value of DeptId otherwise I have to write insert statement without departmentId
IF (EXISTS(
SELECT 1
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = 'Department'
AND column_name = 'DeptId'
))
DECLARE #DeptId UNIQUEIDENTIFIER;
SET #DeptId = Select DeptId From Department Where DeptName = 'Computer'
INSERT INTO Student ([DeptId], [StudentName])
VALUES (#DeptId, 'TBAG')
But as DeptId column sometimes not present I need to create dynamic Sql.
So I created Select statement
DECLARE #sqlCommand nvarchar(1000)
DECLARE #DeptName varchar(75)
declare #DeptId uniqueIdentifier
SET #DeptName = 'Computer'
SET #sqlCommand = 'SELECT #dept=DeptId FROM customers WHERE DeptName = #DeptName'
EXECUTE sp_executesql #sqlCommand, N'#DeptName varchar(50),#dept uniqueIdentifier OUTPUT', #DeptName = #DeptName, #dept=#DeptId OUTPUT
But how to write Insert statement I am not getting

Answer 1

CREATE TABLE dbo.Student
(
DeptId UNIQUEIDENTIFIER,
StudentName VARCHAR(20)
)
GO
DECLARE #DeptId UNIQUEIDENTIFIER
IF COL_LENGTH('dbo.Department', 'DeptId') IS NOT NULL BEGIN
SELECT #DeptId = DeptId
FROM dbo.Department
WHERE DeptName = 'Computer'
END
INSERT INTO dbo.Student(DeptId, StudentName)
SELECT #DeptId /* null is when DeptId is not exists */, 'TBAG'
Output -
(1 row(s) affected)

Answer 2

As per my understanding you want to prepare dynamic insert statement for student table with two cases (with deptid or without deptid)
Please refer the code below.
DECLARE #STUDENTID INT='',--MENTION YOUR STUDENT ID VALUE AND USE THE SAME IN THE ELSE PART COMMENT OUT IF IT HAS IDENTITY
#STUDENTNAME VARCHAR(100)=''--MENTION YOUR STUDENT NAME
IF Col_length('dbo.Student', 'DeptId') IS NOT NULL
BEGIN
INSERT INTO dbo.Student
(DeptId,
StudentName)
SELECT DeptId,
'TBAG'
FROM dbo.Department
WHERE DeptName = 'Computer'
END
ELSE
BEGIN
INSERT INTO dbo.Student
(StudentName)
SELECT #STUDENTNAME
END