The latest articles on DEV Community by Mohd Ansari (@mohd_ansari_ac4dda446b2da). https://dev.to/mohd_ansari_ac4dda446b2da https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F3201685%2Fa0f7e87e-deed-45f8-9837-061ebe6baf4f.png https://dev.to/mohd_ansari_ac4dda446b2da en Mohd Ansari Sat, 24 May 2025 17:00:07 +0000 https://dev.to/mohd_ansari_ac4dda446b2da/difference-between-union-and-union-all-in-sql-1kdk https://dev.to/mohd_ansari_ac4dda446b2da/difference-between-union-and-union-all-in-sql-1kdk <p>Difference between UNION and UNION ALL in SQL<br> Both <code>UNION</code> and <code>UNION ALL</code> are used to combine the result sets of two or more <code>SELECT</code> queries. For both operators, the number of columns, data types of columns, and the order of columns must be the same in the <code>SELECT</code> clause. The <code>ORDER BY</code> clause, if used, must be applied to the last <code>SELECT</code> statement.</p> <p>UNION UNION ALL<br> Removes duplicate rows from the result set. Does not remove duplicate rows; all rows are returned.<br> Generally slower than <code>UNION ALL</code> because it involves sorting and duplicate removal. Generally faster than <code>UNION</code> as it does not perform duplicate removal.<br> When you need a combined list of unique records. When you need all records (including duplicates) and performance is critical.</p> sql