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SQL Null Functions

SQL Null Functions are used to handle null values in SQL databases. Null values are used to represent missing or unknown data in a database. Null values can cause problems when performing calculations or comparisons in SQL queries. SQL Null Functions provide a way to handle null values in a database.

There are several SQL Null Functions that can be used to handle null values in a database. These functions include:

  • IS NULL
  • IS NOT NULL
  • COALESCE
  • NULLIF

IS NULL

The IS NULL function is used to check if a value is null. The syntax for the IS NULL function is:

SELECT column_name
FROM table_name
WHERE column_name IS NULL;

This query will return all rows where the column_name is null.

IS NOT NULL

The IS NOT NULL function is used to check if a value is not null. The syntax for the IS NOT NULL function is:

SELECT column_name
FROM table_name
WHERE column_name IS NOT NULL;

This query will return all rows where the column_name is not null.

COALESCE

The COALESCE function is used to return the first non-null value in a list of values. The syntax for the COALESCE function is:

SELECT COALESCE(column_name1, column_name2, ...)
FROM table_name;

This query will return the first non-null value from column_name1, column_name2, and so on.

NULLIF

The NULLIF function is used to return null if two values are equal. The syntax for the NULLIF function is:

SELECT NULLIF(value1, value2)
FROM table_name;

This query will return null if value1 is equal to value2.

SQL Null Functions are an important part of SQL databases. They provide a way to handle null values in a database and prevent errors in SQL queries. By using SQL Null Functions, you can ensure that your SQL queries are accurate and reliable.

Code Examples

Here are some code examples of SQL Null Functions:

IS NULL

SELECT *
FROM customers
WHERE phone_number IS NULL;

IS NOT NULL

SELECT *
FROM customers
WHERE phone_number IS NOT NULL;

COALESCE

SELECT COALESCE(phone_number, email)
FROM customers;

NULLIF

SELECT NULLIF(phone_number, '555-555-5555')
FROM customers;

References



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