Statement Merge For Free

First, you specify the target table and the source table in the MERGE clause. Second, the merge_condition determines how the rows from the source table are matched to the rows from the target table. It is similar to the join condition in the join clause.

Use the MERGE statement to select rows from one or more sources for update or insertion into one or more tables. It lets you avoid multiple INSERT , UPDATE , and DELETE DML statements.MERGE is a deterministic statement.

Select the same number of columns for each query. Corresponding columns must be the same general data type. Corresponding columns must all either allow null values or not allow null values. If you want to order the columns, specify a column number because the names of the columns you are merging are probably different.

The MERGE statement basically merges data from a source result set to a target table based on a condition that you specify and if the data from the source already exists in the target or not.The MERGE statement basically works as separate INSERT, UPDATE, and DELETE statements all within the same statement.

The MERGE statement was introduced in Oracle 9i to conditionally insert or update data depending on its presence, a process also known as an "upsert". The MERGE statement reduces table scans and can perform the operation in parallel if required.

Starting with SQL Server 2008, you can use a MERGE statement to modify data in a target table based on data in a source table.You can then insert, modify, or delete data from the target table-all in one statement-according to how the rows match up as a result of the join.

The MERGE statement basically works as separate INSERT, UPDATE, and DELETE statements all within the same statement. You specify a "Source" record set and a "Target" table and the JOIN condition between the two.