SQL Functions
What is a function?
A function is a predefined formula which takes one or more arguments as input then process the arguments and returns an output.
SQL function
There are two types of SQL functions, aggregate functions, and scalar(non-aggregate) functions. Aggregate functions operate on many records and produce a summary, works with GROUP BY whereas non-aggregate functions operate on each record independently.
There are so many built-in functions in SQL to do various calculations on data.
Types of SQL functions
| SQL functions | Description |
|---|---|
| SQL Aggregate Function | This function can produce a single value for an entire group or table.
They operate on sets of rows and return results based on groups of rows. Some Aggregate functions are - |
| SQL Arithmetic Function | A mathematical function executes a mathematical operation usually based on input values that are provided as arguments, and return a numeric value as the result of the operation. Mathematical functions operate on numeric data such as decimal, integer, float, real, smallint, and tinyint. Some Arithmetic functions are - |
| SQL Character Function | A character or string function is a function which takes one or more characters or numbers as parameters and returns a character value. Basic string functions offer a number of capabilities and return a string value as a result set. Some Character functions are - |
Practice SQL Exercises
- SQL Exercises, Practice, Solution
- SQL Retrieve data from tables [33 Exercises]
- SQL Boolean and Relational operators [12 Exercises]
- SQL Wildcard and Special operators [22 Exercises]
- SQL Aggregate Functions [25 Exercises]
- SQL Formatting query output [10 Exercises]
- SQL Quering on Multiple Tables [7 Exercises]
- FILTERING and SORTING on HR Database [38 Exercises]
- SQL JOINS
- SQL SUBQUERIES
- SQL Union[9 Exercises]
- SQL View[16 Exercises]
- SQL User Account Management [16 Exercise]
- Movie Database
- BASIC queries on movie Database [10 Exercises]
- SUBQUERIES on movie Database [16 Exercises]
- JOINS on movie Database [24 Exercises]
- Soccer Database
- Introduction
- BASIC queries on soccer Database [29 Exercises]
- SUBQUERIES on soccer Database [33 Exercises]
- Hospital Database
- Employee Database
- More to come!
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SQL: Interview question/Tips of the Day
First Normal Forms
- Eliminate repeating groups in individual tables.
- Create a separate table for each set of related data.
- Identify each set of related data with a primary key.
Do not use multiple fields in a single table to store similar data. For example, to track an inventory item that may come from two possible sources, an inventory record may contain fields for Vendor Code 1 and Vendor Code 2. Also, what happens when you add a third vendor? Adding a field is not the answer; it requires program and table modifications and does not smoothly accommodate a dynamic number of vendors. Instead, place all vendor information in a separate table called Vendors, then link inventory to vendors with an item number key, or vendors to inventory with a vendor code key.
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