Dynamic SQL

Prerequisite – Difference between Static and Dynamic SQL

Dynamic SQL is a programming technique that could be used to write SQL queries during runtime. Dynamic SQL could be used to create general and flexible SQL queries.

Syntax for dynamic SQL is to make it string as below :

'SELECT statement';

To run a dynamic SQL statement, run the stored procedure sp_executesql as shown below :

EXEC sp_executesql N'SELECT statement';

Use prefix N with the sp_executesql to use dynamic SQL as a Unicode string.

Steps to use Dynamic SQL :

1. Declare two variables, @var1 for holding the name of the table and @var 2 for holding the dynamic SQL :

   DECLARE 
   @var1 NVARCHAR(MAX), 
   @var2 NVARCHAR(MAX);

2. Set the value of the @var1 variable to table_name :

   SET @var1 = N'table_name';

3. Create the dynamic SQL by adding the SELECT statement to the table name parameter :

   SET @var2= N'SELECT * 
   FROM ' + @var1;

4. Run the sp_executesql stored procedure by using the @var2 parameter :

   EXEC sp_executesql @var2;

Example –

SELECT * 
from geek;

Table – Geek

ID	NAME	CITY
1	Khushi	Jaipur
2	Neha	Noida
3	Meera	Delhi

Using Dynamic SQL :

DECLARE 
@tab NVARCHAR(128), 
@st NVARCHAR(MAX);
SET @tab = N'geektable';
SET @st = N'SELECT * 
FROM ' + @tab;
EXEC sp_executesql @st;

Table – Geek

ID	NAME	CITY
1	Khushi	Jaipur
2	Neha	Noida
3	Meera	Delhi