Category Archives: sql

SQL – UPDATE JOIN Table of content To update the data entered in a single database table using SQL, you can use the UPDATE statement. However, to update the data in multiple database tables, we need to use the UPDATE… JOIN clause. For instance, if a student changes their primary phone number and wishes to […]

UNION vs JOIN Table of content SQL provides various relational operators to handle data that is spread across multiple tables in a relational database. Out of them, UNION and JOIN queries are fundamentally used to combine data from multiple tables. Even though they are both used for the same purpose, i.e. to combine tables, there […]

SQL – Unique Key Table of content The SQL Unique Key The SQL Unique Key (or, Unique constraint) does not allow duplicate values in a column of a table. It prevents two records from having same values in a column. Unique Key is just an alternative to the Primary Key; as both Unique and Primary […]