Let’s see how to use COALESCE with strings in PostgreSQL. As part of our PostgreSQL Support, Bobcares provides answers to all of your questions.

COALESCE with String in PostgreSQL

An infinite number of arguments can be passed to the COALESCE function. The first parameter that is not null is returned. The COALESCE function will return null if all of the inputs are null. Until it locates the first parameter that is not null, the COALESCE function examines arguments from left to right. The first non-null argument and all subsequent arguments are not examined.

The COALESCE function in PostgreSQL is used to retrieve the first expression in a list of expressions that is not null. Fallback values and handling null values are two typical uses for it. The COALESCE function in PostgreSQL is used to return the function’s first parameter that is not null. When we have numerous expressions or values and want to choose the first one that isn’t null, we can use it frequently. COALESCE functions with strings in the same way as it does with other data types. This is how to apply it to strings: When use COALESCE, the proper syntax is as follows:

Let’s see how to use COALESCE function in PostgreSQL:

In this example, the default_value will be used in place of column_name if it is null.

For multiple expressions, we can also use the below syntax:

Here, the default_value will be used If any of the columns (column1, column2, column3) is null.

Nesting COALESCE

Also, we can nest multiple COALESCE expressions to handle default values hierarchically

SELECT COALESCE(COALESCE(column1, column2), default_value) FROM table_name;

Here, if column1 is null, it will be replaced with column2, and if column2 is also null, the default_value will be returned.

COALESCE With Other Functions

For higher-level processes, COALESCE can be linked to other functions. For example:

SELECT COALESCE(Total(sales), 0) FROM table_name;

In this example, if the total of sales is null, it will be replaced with 0.

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Conclusion

We can easily understand more about the usage of COALESCE with strings in PostgreSQL with this article.