## Introduction

SQL has a many built-in functions to compute string and numeric data.

**The two types of SQL functions are:**
1. SQL Aggregate functions

2. SQL Scalar functions

## SQL Aggregate functions

**1. SQL SUM() Function**

SQL SUM() function is used to compute the total sum of a numeric column of a table.

**Syntax:**
SELECT SUM(Column_name) FROM table_name;
**Example : Query using SUM() Function.**
Consider the following table titled

**'Stationary',** which contains the information of products.

**Write a query to display a Low price from table 'Stationary'.**
ID | Name | Quantity | Price |
---|

1 | Pen | 10 | 200 |

2 | Ink | 15 | 300 |

3 | Notebook | 20 | 400 |

4 | Pencil | 30 | 150 |

SELECT SUM(Price) AS SUM FROM Stationary;
**The result is shown in the following table.**
**2. SQL AVG() Function**

SQL AVG() function is used to compute average value of a numeric column.

**Syntax:**
SELECT AVG (Column name )

FROM table_name

WHERE [Conditions];

**Example : Query using AVG() Function.**
Consider the following table titled

**'Stationary',** which contains the information of products.

ID | Name | Quantity | Price |
---|

1 | Pen | 10 | 200 |

2 | Ink | 15 | 300 |

3 | Notebook | 20 | 400 |

4 | Pencil | 30 | 150 |

**i) Write a query to calculate average price of products**
SELECT AVG(Price)

FROM Stationary;

**The result is shown in the following table as:**
**ii) Write a query to display records(Name and price) of products which are greater than average price in the table.**
SELECT Name, Price FROM Stationary

WHERE Price > (SELECT AVG(Price) FROM Stationary);

**The result is shown in the following table.**
Name | Price |
---|

Ink | 300 |

Notebook | 400 |

**3. SQL COUNT() function**

The SQL COUNT() function is used to return the number of rows, that matches to given query.

**Syntax:**
SELECT COUNT(expression)

FROM table_name

WHERE [conditions];

**Example : Query using COUNT() Function.**
Consider the following table titled

** 'Stationary',** which contains the information of products.

ID | Name | Quantity | Price |
---|

1 | Pen | 10 | 200 |

2 | Ink | 15 | 300 |

3 | Notebook | 20 | 400 |

4 | Pencil | 30 | 150 |

**i) Write a query to count number of values of the column 'Name'**
SELECT COUNT (Name)

FROM Stationary;

**The result is shown in the following table.**
**ii) SELECT COUNT(*) FROM Stationary **
This query is used to return the number of records present in table.

**The result is shown in the following table.**
**iii) SELECT COUNT(DISTINCT Column name) FROM table_name**
This statement is used to count total distinct names of a specific table, as explained below.

SELECT COUNT(DISTINCT Name) FROM Stationary;
**The result is shown in the following table.**