How do you MERGE in SQL?
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.
What is the difference between Merge and update in Oracle?
Both the MERGE and UPDATE statements are designed to modify data in one table based on data from another, but MERGE can do much more. Whereas UPDATE can only modify column values you can use the MERGE statement to synchronize all data changes such as removal and addition of row.
What is MERGE into in SQL?
The MERGE statement in SQL is a very popular clause that can handle inserts, updates, and deletes all in a single transaction without having to write separate logic for each of these. The MERGE statement tries to compare the source table with the target table based on a key field and then do some of the processing.
How does upsert and merge work in Teradata?
Teradata Upsert / Merge. Teradata provide a way to perform Update & Insert operations simultaneously on a table from other table. If update condition matches from another table then update will happen and if not then unmatched rows will be inserted in the table.
What should the error limit be in merge into Teradata?
The value you specify for error_limit can be anything in the range from 1 through 16,000,000, inclusive. The default value for error_limit is 10. MERGE is ANSI SQL:2011-compliant. Note that in the ANSI definition, this statement is named MERGE INTO, while in the Teradata definition, INTO is an optional keyword.
When to update and delete rows in Teradata?
WHEN MATCHED, UPDATE. WHEN NOT MATCHED, INSERT. We can also delete the rows if the record matched by specifying : WHEN MATCHED,DELETE. The source and target table should have the same PI and PPI that helps to process the merge statement faster in Teradata.
How does match _ condition work in Teradata Database?
If the condition is met for any target rows and a WHEN MATCHED clause is specified, then the matching target rows are updated or deleted. match_condition must specify an equality constraint on the primary index of target_table to ensure that the candidate target row set can be hash‑accessed on a single AMP.