Category Archives: sql

SQL – ALTER TABLE Table of content SQL − ALTER TABLE Statement The SQL ALTER TABLE command is a part of Data Definition Language (DDL) and modifies the structure of a table. The ALTER TABLE command can add or delete columns, create or destroy indexes, change the type of existing columns, or rename columns or […]

SQL – Constraints Table of content SQL Constraints SQL Constraints are the rules applied to a data columns or the complete table to limit the type of data that can go into a table. When you try to perform any INSERT, UPDATE, or DELETE operation on the table, RDBMS will check whether that data violates […]

SQL – Expressions Table of content What is SQL Expression? An SQL expression is a combination of one or more values, operators and SQL functions that are all evaluated to a value. These SQL EXPRESSION(s) are like formulae and they are written in query language. You can also use them to query the database for […]