SQL TOP is used to control the amount of rows produced by the SELECT statement. When you are working with big datasets(millions of rows), it is important to keep in mind that SELECT statements use processing power of the system. SQL TOP Limits the rows returned in a query result set to a specified number …
Primary Key A primary key in SQL (Structured Query Language) is a special field or column or combination of columns within a table that uniquely identifies each record (row) in that table. It is used to uniquely identify all the rows of the table. In a table with a primary key, no two rows have …
SQL UNION and UNION ALL are used to combine result sets of two or more SELECT statements. Syntax: When we use only UNION , duplicate values are removed.When we use UNION ALL, ALL values are present and duplicates are not removed. EXAMPLE: To give a demo of UNION, we are going to use table ‘PLAYERS_LOCATION’ …
In SQL, unique constraint keep in check that all values of a column or columns are unique. Unique constraints make sure no duplicate values are present in the database table. Syntax: Here are some characteristics of unique constraint- Primary key vs Unique Constraint Both Primary key and unique constraint are used in DBMS to ensure …
In SQL, NOT NULL constraints are used to ensure that column(s) do not accept NULL values. Sometimes it is important to ensure no NULL values are present in table. Syntax: Above code will make sure zero NULL values are present in columns i.e. first_name, last_name and email. Here are the uses of NOT NULL Constraint …
SQL LEAD Function SQL LEAD function is used by the user if he wants to check or compare value present in the next rows With the current row. Syntax: The first argument of LEAD function is the column name from which you want to fetch the value. The offset value is the number of rows …
What are SQL CTE? SQL CTE or common table expressions are temporary tables created by the result of some other query. They have their name and can be referenced in SQL statements.They are created using WITH clause encapsulating SQL statements. Syntax Of CTE: EXAMPLE: For Example we are going to use the EMPLOYEE table. For …
SQL Common Table Expression(CTE) -CLEAR And PRECISE Read More »
SQL views are virtual tables created by the user. SQL views can also be considered as a subset of tables.SQL views provide security features to users as they can be used to keep the main table safe or inaccessible to others. Syntax of Views: Updating View: Dropping View: EXAMPLE: We will use the following table …
What is subquery? Subqueries in SQL are queries inside queries. Users can specify a Query in either the FROM clause or WHERE clause. The internal query filters rows and makes it easier for the external query to operate. You can bypass the use of subquery but it will make the query long with less readability. …
SQL SubQueries Basic- What are they? How to use them ? Read More »
What are SQL joins? SQL GROUP BY is used to group rows with similar values for aggregate functions. Without GROUP BY user cannot use aggregate functions. Syntax: Now lets use GROUP BY with HAVING Thanks For Reading! SOURCE : https://learn.microsoft.com/en-us/sql/t-sql/queries/select-group-by-transact-sql?view=sql-server-ver16 READ MORE:SQL BASICSSQL WINDOW FUNCTIONSSQL ORDER BY
