DML (Data Manipulation Language) commands in SQL are used to manipulate and work with data within a database. These commands enable you to insert, update, delete, and retrieve data from database tables. The primary DML commands in SQL are:
SELECT: The SELECT statement retrieves data from one or more tables or views in the database. It allows you to specify the columns you want to retrieve, apply filters with conditions using the WHERE clause, sort the result set with the ORDER BY clause, and perform various other operations like joining tables, aggregating data with functions (e.g., SUM, AVG), and grouping data with the GROUP BY clause.
INSERT: The INSERT statement is used to add new rows of data into a table. It allows you to specify the values for each column or select values from another table or subquery to insert into the target table.
UPDATE: The UPDATE statement modifies existing data in a table. It allows you to specify the table, set the new values for specific columns, and apply conditions using the WHERE clause to determine which rows should be updated.
DELETE: The DELETE statement removes one or more rows from a table. It allows you to specify the table and apply conditions using the WHERE clause to determine which rows should be deleted.
MERGE: The MERGE statement combines the functionality of INSERT, UPDATE, and DELETE into a single statement. It allows you to perform conditional inserts or updates based on whether a row already exists or not, making it useful for implementing upsert (insert or update) operations.
These DML commands are fundamental for manipulating data within a database, allowing you to insert new data, update existing data, delete unwanted data, and retrieve specific data based on various criteria.