Postgres Concat_ws - SQL

Introduction

PostgreSQL is an open-source relational database management system that has gained popularity in recent years. It provides various SQL functions to manipulate data and generate reports. One of the essential SQL functions in PostgreSQL is CONCAT_WS.

CONCAT_WS (Concatenate With Separator) is a string processing function that concatenates and separates string elements based on the specified separator. The first argument of the CONCAT_WS function is the separator, followed by the string values to be concatenated. The separator value can be any character or string.

In this article, we will explore the CONCAT_WS function usage in PostgreSQL.

Syntax

CONCAT_WS(separator, string1, string2, ..., stringN)

Example

SELECT CONCAT_WS('-', 'John', 'Doe');

Output:

John-Doe

In this example, the two string values 'John' and 'Doe' are concatenated with a separator '-' using the CONCAT_WS function.

More Examples

Concatenating Multiple Columns with Separator

It is quite common to concatenate multiple columns from a table. The CONCAT_WS function makes this task simpler. For instance, consider a table with Name, Address, and City columns. We want to concatenate all these columns as a single string value with a separator ','.

SELECT CONCAT_WS(',', Name, Address, City) as FullAddress
FROM Customers;

Output:

FullAddress
-------------------------------------------------------
John,The Avenue,New York
Doe,Park Street,London
Karen,Baker Street,London

Concatenating Various Column Values Based on a Condition

Sometimes, we may want to concatenate specific column values in a table based on certain conditions. For instance, suppose we have a table with 4 columns, namely 'id,' 'cust_name,' 'phone_no,' and 'alt_phone_no.' We want to concatenate 'phone_no' and 'alt_phone_no' column values if the 'alt_phone_no' value is not null. Otherwise, we only concatenate 'phone_no' column value.

SELECT CONCAT_WS(',', cust_name, phone_no,
   CASE WHEN alt_phone_no IS NOT NULL THEN alt_phone_no ELSE '' END) as PhoneNumbers
FROM CustomerDetails;

Output:

PhoneNumbers
--------------------------------
John,123456789,
Doe,987654321,+449876543
Karen,764738294,

In the above query, we used CASE statement logic to handle the null value of 'alt_phone_no' column.

Conclusion

CONCAT_WS is a powerful PostgreSQL function that simplifies string concatenation and separation operations within SQL queries. It is quite helpful in generating reports and in data manipulation.