jQuery Tutorial

"Try it yourself" Examples in Each Chapter

With our online editor, you can edit the code, and click on a button to view the result.

Example

$(document).ready(function(){
  $("p").click(function(){
    $(this).hide();
  });
});

Try it yourself »

Click on the "Try it yourself" button to see how it works.

---

jQuery Examples

Learn by examples! At W3Schools you will find a lot of jQuery examples to edit and test yourself.

• jQuery Examples

---

jQuery References

At W3Schools you will find a complete reference of all jQuery objects and methods.

• jQuery Reference

SQL MAX() Function

The MAX() Function

The MAX() function returns the largest value of the selected column.

SQL MAX() Syntax

SELECT MAX(column_name) FROM table_name;

---

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Products" table:

ProductID	ProductName	SupplierID	CategoryID	Unit	Price
1	Chais	1	1	10 boxes x 20 bags	18
2	Chang	1	1	24 - 12 oz bottles	19
3	Aniseed Syrup	1	2	12 - 550 ml bottles	10
4	Chef Anton's Cajun Seasoning	2	2	48 - 6 oz jars	21.35
5	Chef Anton's Gumbo Mix	2	2	36 boxes	25

---

SQL MAX() Example

The following SQL statement gets the largest value of the "Price" column from the "Products" table:

Example

SELECT MAX(Price) AS HighestPrice FROM Products;

Try it yourself »

SQL LAST() Function

The LAST() Function

The LAST() function returns the last value of the selected column.

SQL LAST() Syntax

SELECT LAST(column_name) FROM table_name;

Note: The LAST() function is only supported in MS Access.

---

SQL LAST() Workaround in SQL Server, MySQL and Oracle

SQL Server Syntax

SELECT TOP 1 column_name FROM table_nameORDER BY column_name DESC;

Example

SELECT TOP 1 CustomerName FROM Customers
ORDER BY CustomerID DESC;

MySQL Syntax

SELECT column_name FROM table_name
ORDER BY column_name DESC
LIMIT 1;

Example

SELECT CustomerName FROM Customers
ORDER BY CustomerID DESC
LIMIT 1;

Oracle Syntax

SELECT column_name FROM table_name
ORDER BY column_name DESC
WHERE ROWNUM <=1;

Example

SELECT CustomerName FROM Customers
ORDER BY CustomerID DESC
WHERE ROWNUM <=1;

---

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Customers" table:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

---

SQL LAST() Example

The following SQL statement selects the last value of the "CustomerName" column from the "Customers" table:

Example

SELECT LAST(CustomerName) AS LastCustomer FROM Customers;

Try it yourself »

SQL FIRST() Function

The FIRST() Function

The FIRST() function returns the first value of the selected column.

SQL FIRST() Syntax

SELECT FIRST(column_name) FROM table_name;

Note: The FIRST() function is only supported in MS Access.

---

SQL FIRST() Workaround in SQL Server, MySQL and Oracle

SQL Server Syntax

SELECT TOP 1 column_name FROM table_nameORDER BY column_name ASC;

Example

SELECT TOP 1 CustomerName FROM Customers
ORDER BY CustomerID ASC;

MySQL Syntax

SELECT column_name FROM table_name
ORDER BY column_name ASC
LIMIT 1;

Example

SELECT CustomerName FROM Customers
ORDER BY CustomerID ASC
LIMIT 1;

Oracle Syntax

SELECT column_name FROM table_name
ORDER BY column_name ASC
WHERE ROWNUM <=1;

Example

SELECT CustomerName FROM Customers
ORDER BY CustomerID ASC
WHERE ROWNUM <=1;

---

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Customers" table:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

---

SQL FIRST() Example

The following SQL statement selects the first value of the "CustomerName" column from the "Customers" table:

Example

SELECT FIRST(CustomerName) AS FirstCustomer FROM Customers;

Try it yourself »

SQL COUNT() Function

The COUNT() function returns the number of rows that matches a specified criteria.

---

SQL COUNT(column_name) Syntax

The COUNT(column_name) function returns the number of values (NULL values will not be counted) of the specified column:

SELECT COUNT(column_name) FROM table_name;

SQL COUNT(*) Syntax

The COUNT(*) function returns the number of records in a table:

SELECT COUNT(*) FROM table_name;

SQL COUNT(DISTINCT column_name) Syntax

The COUNT(DISTINCT column_name) function returns the number of distinct values of the specified column:

SELECT COUNT(DISTINCT column_name) FROM table_name;

Note: COUNT(DISTINCT) works with ORACLE and Microsoft SQL Server, but not with Microsoft Access.

---

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Orders" table:

OrderID	CustomerID	EmployeeID	OrderDate	ShipperID
10265	7	2	1996-07-25	1
10266	87	3	1996-07-26	3
10267	25	4	1996-07-29	1

---

SQL COUNT(column_name) Example

The following SQL statement counts the number of orders from "CustomerID"=7 from the "Orders" table:

Example

SELECT COUNT(CustomerID) AS OrdersFromCustomerID7 FROM Orders
WHERE CustomerID=7;

Try it yourself »

---

SQL COUNT(*) Example

The following SQL statement counts the total number of orders in the "Orders" table:

Example

SELECT COUNT(*) AS NumberOfOrders FROM Orders;

Try it yourself »

---

SQL COUNT(DISTINCT column_name) Example

The following SQL statement counts the number of unique customers in the "Orders" table:

Example

SELECT COUNT(DISTINCT CustomerID) AS NumberOfCustomers FROM Orders;

Try it yourself »

SQL AVG() Function

The AVG() Function

The AVG() function returns the average value of a numeric column.

SQL AVG() Syntax

SELECT AVG(column_name) FROM table_name

---

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Products" table:

ProductID	ProductName	SupplierID	CategoryID	Unit	Price
1	Chais	1	1	10 boxes x 20 bags	18
2	Chang	1	1	24 - 12 oz bottles	19
3	Aniseed Syrup	1	2	12 - 550 ml bottles	10
4	Chef Anton's Cajun Seasoning	2	2	48 - 6 oz jars	21.35
5	Chef Anton's Gumbo Mix	2	2	36 boxes	25

---

SQL AVG() Example

The following SQL statement gets the average value of the "Price" column from the "Products" table:

Example

SELECT AVG(Price) AS PriceAverage FROM Products;

Try it yourself »

The following SQL statement selects the "ProductName" and "Price" records that have an above average price:

Example

SELECT ProductName, Price FROM Products
WHERE Price>(SELECT AVG(Price) FROM Products);

Try it yourself »

SQL Functions

SQL has many built-in functions for performing calculations on data.

---

SQL Aggregate Functions

SQL aggregate functions return a single value, calculated from values in a column.

Useful aggregate functions:

• AVG() - Returns the average value
• COUNT() - Returns the number of rows
• FIRST() - Returns the first value
• LAST() - Returns the last value
• MAX() - Returns the largest value
• MIN() - Returns the smallest value
• SUM() - Returns the sum

---

SQL Scalar functions

SQL scalar functions return a single value, based on the input value.

Useful scalar functions:

• UCASE() - Converts a field to upper case
• LCASE() - Converts a field to lower case
• MID() - Extract characters from a text field
• LEN() - Returns the length of a text field
• ROUND() - Rounds a numeric field to the number of decimals specified
• NOW() - Returns the current system date and time
• FORMAT() - Formats how a field is to be displayed

Tip: The aggregate functions and the scalar functions will be explained in details in the next chapters.