Pivot in SQL

In SQL, the PIVOT operation is a powerful tool for transforming rows into columns. It’s particularly useful when you want to aggregate data and present it in a more structured format. The PIVOT operation involves specifying an aggregate function and creating new columns based on unique values from a specified column.

Main Concept:

The main concept behind converting rows to columns in SQL is to transpose the data. This means that we will be changing the orientation of the data from a vertical format (rows) to a horizontal format (columns). This can be achieved using the PIVOT function in SQL. The syntax for the PIVOT function is as follows:

Syntax:

SELECT
    [non-pivoted column(s)],
    [pivoted column1],
    [pivoted column2],
    ...
FROM
    [table_name]
PIVOT
(
    aggregate_function(column_name)
    FOR [pivot_column] IN ([value1], [value2], [value3], ...)
) AS [alias_name];

Explanation:

Let’s break down the syntax and understand each component:

• SELECT: This is used to specify the columns we want to retrieve from the table.
• [non-pivoted column(s)]: Columns that remain unchanged and appear in the final result.
• [pivot_column]: The column whose unique values will become new columns in the result.
• FROM: This specifies the table from which we want to retrieve data.
• PIVOT: This is the keyword that tells SQL we want to pivot the data.
• aggregate_function: This is used to perform an aggregate function on the data, such as SUM, COUNT, or AVG.
• aggregate_function(column_name): The aggregate function to be applied to the values in the pivoted column.
• column_name: This is the column on which we want to perform the aggregate function.
• pivot_column: This is the column that will become the new column headers.
• [value1], [value2], [value3], … : The unique values from the pivot column that will be transformed into new columns.
• [alias_name]: An alias for the resulting pivoted table.

In SQL, rows and columns are the fundamental building blocks of a database. Rows represent individual records, while columns represent the attributes or characteristics of those records. However, there may be instances where we need to convert rows to columns in order to better analyze and manipulate data. This process is known as “pivoting” and can be done efficiently using SQL. In this article, we will explore the concept of converting rows to columns in SQL and provide step-by-step instructions on how to do it.