How Can I Effectively Use Declared Variables with IN Clauses in SQL Server to Avoid Conversion Errors?

Handling IN clauses using IN clauses declaring variables in SQL Server

Inserting multiple values ​​into an IN clause using declared variables may encounter errors, especially if the variable contains non-numeric characters. Let's explore this problem and discuss a solution.

Understanding error

In the given SQL statement:

<code class="language-sql">DECLARE @ExcludedList VARCHAR(MAX)

SET @ExcludedList = 3 + ', ' + 4 + ' ,' + '22'

SELECT * FROM A WHERE Id NOT IN (@ExcludedList)</code>

The error message indicates that the conversion from a VARCHAR value containing commas and spaces to an integer (INT) failed. This is because the IN clause expects a range of numeric values, and commas and spaces are not recognized as valid integers.

Use table variables to process dynamic lists

One way to overcome this limitation is to use a table variable to store the list of values ​​for the IN clause. This allows us to insert multiple values ​​into a table variable and treat it as a single entity.

Create and populate table variables

Declare a table variable to represent the list of excluded values:

<code class="language-sql">DECLARE @ExcludedList TABLE (Id INT)</code>

Insert values ​​into table variables using a loop or any other appropriate method:

<code class="language-sql">INSERT INTO @ExcludedList VALUES (3)
INSERT INTO @ExcludedList VALUES (4)
INSERT INTO @ExcludedList VALUES (22)</code>

Use table variables in IN clause

IN clauses can now reference table variables, which will automatically handle the conversion of their values ​​to integers:

<code class="language-sql">SELECT * FROM A WHERE Id NOT IN (SELECT Id FROM @ExcludedList)</code>

This modified statement will return rows from table A that are not in the exclude list, thus avoiding conversion errors.

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