Category: SQL

SQL unique constraint is a type of constraint that ensures that the data in a column or set of columns is unique across all rows in a table. It is used to prevent duplicate values from being inserted into a table and to ensure data integrity. To create a unique constraint in SQL, you can…(Continue Reading)

A foreign key constraint in SQL is a type of constraint that is used to establish a link between two tables in a relational database. This constraint ensures that the data being stored in the child table (the table that contains the foreign key) is consistent with the data in the parent table (the table…(Continue Reading)

In SQL, a primary key constraint is used to define a column or a set of columns that uniquely identify each row in a table. It is a type of constraint that helps enforce data integrity by preventing duplicate or null values in the primary key column(s). The primary key constraint is specified at the…(Continue Reading)

SQL TRUNCATE TABLE is a command used in Structured Query Language (SQL) to delete all the data from a table in a database. The TRUNCATE TABLE statement is a data manipulation language (DML) command that can be used to remove all the data from a table quickly and efficiently. When you use the TRUNCATE TABLE…(Continue Reading)

SQL is a standard language used for managing relational databases. It provides a wide range of commands and functions to perform various operations on a database. One of the essential commands in SQL is DROP TABLE, which is used to delete a table from a database. Syntax The syntax for using the DROP TABLE command…(Continue Reading)

SQL ALTER TABLE is a statement that allows you to modify the structure of an existing database table. This can include changing the name of the table, adding or removing columns, modifying the data type or length of a column, and setting constraints on the table. The syntax for the ALTER TABLE statement varies depending…(Continue Reading)

The SQL HAVING clause is a component of the SQL SELECT statement that allows you to filter the results of an aggregation based on a specific condition. In other words, it enables you to apply conditions to grouped data after the GROUP BY clause has been applied. The HAVING clause is similar to the WHERE…(Continue Reading)

The GROUP BY clause is a powerful feature of the Structured Query Language (SQL) that allows you to group the result set of a query by one or more columns. This clause is commonly used in combination with aggregate functions, such as COUNT, SUM, AVG, MIN, and MAX, to calculate summary statistics for each group.…(Continue Reading)

The SQL ORDER BY clause is used to sort the result set of a SELECT statement in a specified order. It allows you to sort the rows returned by a query based on one or more columns. The syntax for the ORDER BY clause is: SELECT column1, column2, … FROM table_name ORDER BY column1 [ASC|DESC],…(Continue Reading)

SQL LIKE is a clause used in SQL statements to search for patterns in a database. It is used in conjunction with the SELECT, UPDATE, and DELETE statements to filter records based on a specified pattern. The LIKE operator is often used to search for a specific string of characters within a column in a…(Continue Reading)