SQL – TRUNCATE TABLE Command
The SQL TRUNCATE TABLE command is used to delete complete data from an existing table. You can also use DROP TABLE command to delete complete table but it would remove complete table…
SQL – ALTER TABLE Command
The SQL ALTER TABLE command is used to add, delete or modify columns in an existing table. You should also use the ALTER TABLE command to add and drop various constraints on…
SQL – Indexes
Indexes are special lookup tables that the database search engine can use to speed up data retrieval. Simply put, an index is a pointer to data in a table. An index in…
SQL – Alias Syntax
You can rename a table or a column temporarily by giving another name known as Alias. The use of table aliases is to rename a table in a specific SQL statement.…
SQL – NULL Values
The SQL NULL is the term used to represent a missing value. A NULL value in a table is a value in a field that appears to be blank. A field with…
SQL – UNIONS CLAUSE
The SQL UNION clause/operator is used to combine the results of two or more SELECT statements without returning any duplicate rows. To use this UNION clause, each SELECT statement must…
SQL – Using Joins
The SQL Joins clause is used to combine records from two or more tables in a database. A JOIN is a means for combining fields from two tables by using values common…
SQL – Constraints
Constraints are the rules enforced on the data columns of a table. These are used to limit the type of data that can go into a table. This ensures the…
SQL – SORTING Results
The SQL ORDER BY clause is used to sort the data in ascending or descending order, based on one or more columns. Some databases sort the query results in an ascending order…
SQL – Distinct Keyword
The SQL DISTINCT keyword is used in conjunction with the SELECT statement to eliminate all the duplicate records and fetching only unique records. There may be a situation when you have multiple…