SQL Server String DATALENGTH() Function

SQL Server DATALENGTH() Function

The SQL Server DATALENGTH() function is used to return the number of bytes used to represent any expression. This function is useful for determining the storage size of various data types, including text, binary, and image data.

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Syntax

SELECT DATALENGTH(expression);

The DATALENGTH() function takes a single argument:

• expression: The expression whose byte length is to be calculated.

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Example SQL Server DATALENGTH() Function Queries

Let's look at some examples of SQL Server DATALENGTH() function queries:

1. Basic DATALENGTH() Example

SELECT DATALENGTH('Hello') AS length;

This query returns the number of bytes used to represent the string 'Hello'. The result will be:

length
------
5

2. DATALENGTH() with a Column

SELECT first_name, DATALENGTH(first_name) AS length
FROM employees;

This query returns the byte length of the first_name column for each employee.

3. DATALENGTH() with Different Data Types

SELECT DATALENGTH(CAST(12345 AS VARBINARY)) AS length;

This query returns the number of bytes used to represent the integer value 12345 when cast to a VARBINARY data type. The result will be:

length
------
2

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Full Example

Let's go through a complete example that includes creating a table, inserting data, and using the DATALENGTH() function.

Step 1: Creating a Table

This step involves creating a new table named example_table to store some sample data.

CREATE TABLE example_table (
    id INT PRIMARY KEY,
    description VARCHAR(50)
);

In this example, we create a table named example_table with columns for id and description.

Step 2: Inserting Data into the Table

This step involves inserting some sample data into the example_table.

INSERT INTO example_table (id, description) VALUES (1, 'Apple');
INSERT INTO example_table (id, description) VALUES (2, 'Banana');
INSERT INTO example_table (id, description) VALUES (3, 'Cherry');

Here, we insert data into the example_table.

Step 3: Using the DATALENGTH() Function

This step involves using the DATALENGTH() function to calculate the byte length of the description column.

SELECT id, description, DATALENGTH(description) AS length
FROM example_table;

This query retrieves the id, description, and the byte length of the description column for each row in the example_table. The result will be:

id  description  length
--- ------------ ------
1   Apple        5
2   Banana       6
3   Cherry       6

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Conclusion

The SQL Server DATALENGTH() function is a powerful tool for determining the storage size of various data types. Understanding how to use the DATALENGTH() function and its syntax is essential for effective data processing and storage management in SQL Server.