Definition of PostgreSQL NULLIF
PostgreSQL nullif is a common conditional expression used to handle null values or expressions in PostgreSQL. nullif also used with the coalesce function to handle the null values. PostgreSQL nullif function returns a null value if provided expressions are equal. If two expressions provided are equal then it provides null value as a result otherwise it will return the first expression as a result.
Syntax:
Below is the syntax of nullif function is as follows.
Select (Argument1 (First value which is used to handle null values), Argument2 (Second value which is used to handle null values))
SELECT Column1, …, ColumnN
COALESCE (
NULLIF (Column_name, ''), )
FROM table_name;
Parameter:
- Select: Select is used to fetch data from the table by using a nullif function in PostgreSQL. We can use multiple column or single column at one time to fetch data from the table.
- Coalesce: Coalesce is states that function name in PostgreSQL which returns as first non-null value as a result. Coalesce function is very important and useful in PostgreSQL.
We have used coalesce function with nullif function in PostgreSQL.
- Argument 1 to Argument 2: Argument is nothing but an integer or character value that we have passing with nullif function. If we have passing two argument and both contains different value then nullif function will return first value in a result. If we have passing both same value then it will return a null values in a result.
- Column 1 to Column N: This is a column name of table. If we want to fetch data from table using nullif function in PostgreSQL then we pass a multiple column at one time. Also we have given column name with nullif function in PostgreSQL.
- From: From is keyword in PostgreSQL used with table name in select query.
- Table name: Table name used with nullif function to fetch data from table.
- Nullif: It is used to handle null values in PostgreSQL, nullif also used with the coalesce function to handle the null values. nullif function returns a null values if provided expressions are equal, If provided two expressions are equal then it provide null value as a result otherwise it will return first expression as a result.
How NULLIF Function Works in PostgreSQL?
Below is the working of nullif function in PostgreSQL.
- We can used coalesce function with nullif function in PostgreSQL. Coalesce is states that function name in PostgreSQL which returns as first non-null value as a result. Coalesce function is very important and useful in PostgreSQL.
- Nullif is a common conditional expression which was used to handle null values or expressions in PostgreSQL.
- If we have passing two argument in nullif function and first contains null value then nullif function will return first value in a result. If we have passing both same value then it will return a null values in a result.
- We have used nullif function in PostgreSQL to prevent error of division by zero.
- Nullif function is used to prevent the error of which is occurred in comparison of two values in PostgreSQL.
Examples of PostgreSQL NULLIF
Below is the example of nullif function.
- We have using a discount table to describe example of nullif function are as follows.
- Below is the data description of discount table which we have used to describe example of nullif function in PostgreSQL.
Example #1
testing=# select * from discount;
Output:
Example #2
In below example we have passing values as 50 and 50. Nullif function will return null values because both the arguments which we have passing are same.
testing=# select nullif (50, 50);
Output:
In above example we have passing same argument with nullif function so it will return null value as a result.
Example #3
In below example we have passing values as 50 and 100. Nullif function will return first value i.e. 50 because both the arguments which we have passing are different.
testing=# select nullif (50, 100);
Output:
In above example we have passing different argument with nullif function so it will return first value as a result.
Example #4
In below example we have passing values as A and P. Nullif function will return first value i.e. A because both the arguments which we have passing are different.
testing=# select nullif (‘A’, ‘P’);
Output:
In above example we have passing different argument with nullif function so it will return first value as a result.
Example #5
In below example we have retrieving data from discount table using nullif function.
testing=# SELECT cust_id, product_name, COALESCE ( NULLIF (Product_price, '')) AS Product_price FROM discount;
Output:
Recommended Articles
This is a guide to PostgreSQL NULLIF. Here we also discuss the Introduction and how nullif function works in PostgreSQL along with different examples and its code implementation. You may also have a look at the following articles to learn more –
