How Can I Efficiently Merge Rows in SQL to Combine Data?

Merging Rows Efficiently in SQL

In SQL, it is often required to combine information from multiple rows into a single consolidated row. Consider the following table:

FK | Field1 | Field2
=====================
3  | ABC    | *NULL*
3  | *NULL* | DEF

To obtain a merged row, it is possible to utilize aggregate functions such as MAX or MIN. These functions ignore NULL values, allowing us to combine non-null values from different rows.

The following query demonstrates the use of the MAX aggregate function to merge the two rows:

SELECT
    FK,
    MAX(Field1) AS Field1,
    MAX(Field2) AS Field2
FROM
    table1
GROUP BY
    FK;

In SQL Server Express 2008 R2, this query produces the following result:

FK  Field1  Field2
--  ------  ------
3   ABC     DEF

This query effectively merges the two rows into a single consolidated row, preserving the FK column and combining the non-null values for Field1 and Field2.

The above is the detailed content of How Can I Efficiently Merge Rows in SQL to Combine Data?. For more information, please follow other related articles on the PHP Chinese website!