SQL - BETWEEN Operator Example

The following SQL statement selects all products with a price BETWEEN 10 and 20:

Example

SELECT * FROM Products
WHERE Price BETWEEN 10 AND 20;

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SQL - IN Operator Example

The following SQL statement selects all customers with a City of "Paris" or "London":

Example

SELECT * FROM Customers
WHERE City IN ('Paris','London');

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SQL - LIKE Operator Examples

The following SQL statement selects all customers with a City starting with the letter "s":

Example

SELECT * FROM Customers
WHERE City LIKE 's%';

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Tip: The "%" sign is used to define wildcards (missing letters) both before and after the pattern. You will learn more about wildcards in the next chapter.

The following SQL statement selects all customers with a City ending with the letter "s":

Example

SELECT * FROM Customers
WHERE City LIKE '%s';

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The following SQL statement selects all customers with a Country containing the pattern "land":

Example

SELECT * FROM Customers
WHERE Country LIKE '%land%';

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Using the NOT keyword allows you to select records that do NOT match the pattern.

The following SQL statement selects all customers with Country NOT containing the pattern "land":

Example

SELECT * FROM Customers
WHERE Country NOT LIKE '%land%';

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SQL - Delete All Data

It is possible to delete all rows in a table without deleting the table. This means that the table structure, attributes, and indexes will be intact:

DELETE FROM table_name;

or

DELETE * FROM table_name;

Note: Be very careful when deleting records. You cannot undo this statement!

SQL - DELETE Example

Assume we wish to delete the customer "Alfreds Futterkiste" from the "Customers" table.

We use the following SQL statement:

Example

DELETE FROM Customers
WHERE CustomerName='Alfreds Futterkiste' AND ContactName='Maria Anders';

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SQL - Update Warning!

Be careful when updating records. If we omit the WHERE clause, ALL records will be updated:

Example

UPDATE Customers
SET ContactName='Juan';

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SQL - UPDATE Multiple Records

In an update statement, it is the WHERE clause that determines how many records which will be updated.

The WHERE clause: WHERE Country='Mexico' will update all records which have the value "Mexico" in the field "Country".

Example

UPDATE Customers
SET ContactName='Juan'
WHERE Country='Mexico';

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SQL - UPDATE Multiple Columns

To update more than one column, use a comma as seperator.

Assume we wish to update the customer "Alfreds Futterkiste" with a new contact person and city.

We use the following SQL statement:

Example

UPDATE Customers
SET ContactName='Alfred Schmidt', City='Frankfurt'
WHERE CustomerID=1;

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SQL - ORDER BY Several Columns Example 2

The following SQL statement selects all customers from the "Customers" table, sorted ascending by the "Country" and descending by the "CustomerName" column:

Example

SELECT * FROM Customers
ORDER BY Country ASC, CustomerName DESC;

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SQL - ORDER BY Several Columns Example

The following SQL statement selects all customers from the "Customers" table, sorted by the "Country" and the "CustomerName" column:

Example

SELECT * FROM Customers
ORDER BY Country, CustomerName;

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SQL - ORDER BY DESC Example

The following SQL statement selects all customers from the "Customers" table, sorted DESCENDING by the "Country" column:

Example

SELECT * FROM Customers
ORDER BY Country DESC;

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SQL - ORDER BY Example

The following SQL statement selects all customers from the "Customers" table, sorted by the "Country" column:

Example

SELECT * FROM Customers
ORDER BY Country;

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SQL - Combining AND & OR

You can also combine AND and OR (use parenthesis to form complex expressions).

The following SQL statement selects all customers from the country "Germany" AND the city must be equal to "Berlin" OR "München", in the "Customers" table:

Example

SELECT * FROM Customers
WHERE Country='Germany'
AND (City='Berlin' OR City='München');

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SQL - OR Operator Example

The following SQL statement selects all customers from the city "Berlin" OR 

"München", in the "Customers" table: 

Example

SELECT * FROM Customers
WHERE City='Berlin'
OR City='München';

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SQL - AND Operator Example

The following SQL statement selects all customers from the country "Germany" AND the city "Berlin", in the "Customers" table:

Example

SELECT * FROM Customers
WHERE Country='Germany'
AND City='Berlin';

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SQL - Operators in The WHERE Clause

The following operators can be used in the WHERE clause:

Operator	Description
=	Equal
<>	Not equal.
>	Greater than
<	Less than
>=	Greater than or equal
<=	Less than or equal
BETWEEN	Between an inclusive range
LIKE	Search for a pattern
IN	To specify multiple possible values for a column

SQL - Text Fields vs. Numeric Fields

SQL requires single quotes around text values (most database systems will also allow double quotes).

However, numeric fields should not be enclosed in quotes:

Example

SELECT * FROM Customers
WHERE CustomerID=1;

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SQL - WHERE Clause Example

The following SQL statement selects all the customers from the country "Mexico", in the "Customers" table:

Example

SELECT * FROM Customers
WHERE Country='Mexico';

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SQL - SELECT DISTINCT Example

The following SQL statement selects only the distinct values from the "City" columns from the "Customers" table:

Example

SELECT DISTINCT City FROM Customers;

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SQL - SELECT * Example

The following SQL statement selects all the columns from the "Customers" table:

Example

SELECT * FROM Customers;

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SQL - SELECT Column Example

The following SQL statement selects the "CustomerName" and "City" columns from the "Customers" table:

Example

SELECT CustomerName,City FROM Customers;

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SQL - Comments in Statements

To ignore just a part of a statement, use the /* */ comment.

Any text between /* and */ will be ignored.

Example

Ignore part of a line:

SELECT CustomerName, /*City,*/ Country FROM Customers;

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Example

Ignore a parts of a statment:

SELECT * FROM Customers WHERE (CustomerName LIKE 'L%'
OR CustomerName LIKE 'R%' /*OR CustomerName LIKE 'S%'
OR CustomerName LIKE 'T%'*/ OR CustomerName LIKE 'W%')
AND Country='USA'
ORDER BY CustomerName;

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SQL - Multi-line Comments

Multi-line comments start with /* and end with */.

Any text between /* and */ will be ignored.

Example

A multi-line comment as an explanation:

/*Select all the columns
of all the records
in the Customers table:*/
SELECT * FROM Customers;

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Example

A multi-line comment to ignore many statements:

/*SELECT * FROM Customers;
SELECT * FROM Products;
SELECT * FROM Orders;
SELECT * FROM Categories;*/
SELECT * FROM Suppliers;

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SQL - Single Line Comments

Single line comments start with --.

Any line between -- and the end of the line will be ignored (will not be executed).

Example

A single-line comment as an explanation:

--Select all:SELECT * FROM Customers;

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Example

A single-line comment to ignore the end of a line:

SELECT * FROM Customers -- WHERE City='Berlin';

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Example

A single-line comment to ignore a statement:

--SELECT * FROM Customers;SELECT * FROM Products;

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Some of The Most Important SQL Commands

• SELECT - extracts data from a database

• UPDATE - updates data in a database

• DELETE - deletes data from a database

• INSERT INTO - inserts new data into a database

• CREATE DATABASE - creates a new database

• ALTER DATABASE - modifies a database

• CREATE TABLE - creates a new table

• ALTER TABLE - modifies a table

• DROP TABLE - deletes a table

• CREATE INDEX - creates an index (search key)

• DROP INDEX - deletes an index

HTML Form - The Submit Button

<input type="submit"> defines a button for submitting the form data to a form-handler.

The form-handler is typically a server page with a script for processing input data.

The form-handler is specified in the form's action attribute:

Example

<form action="action_page.php">
  First name:<br>
  <input type="text" name="firstname" value="Mickey"><br>
  Last name:<br>
  <input type="text" name="lastname" value="Mouse"><br><br>
  <input type="submit" value="Submit">
</form>

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This is how the HTML code above will be displayed in a browser:

First name:
 
Last name:
 

HTML Form - Radio Button Input

<input type="radio"> defines a radio button.

Radio buttons let a user select ONE of a limited number of choices:

Example

<form>
  <input type="radio" name="gender" value="male" checked> Male<br>
  <input type="radio" name="gender" value="female"> Female<br>
  <input type="radio" name="gender" value="other"> Other
</form>

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This is how the HTML code above will be displayed in a browser:

 Male
 Female
 Other

Following tips

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Get direct mail to you about new posts and updates.

Thanking You

Abhishek Gupta

HTML Form - Text Input

<input type="text"> defines a one-line input field for text input:

Example

<form>
  First name:<br>
  <input type="text" name="firstname"><br>
  Last name:<br>
  <input type="text" name="lastname">
</form>

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This is how it will look like in a browser:

First name:

Last name:

Note: The form itself is not visible. Also note that the default width of a text field is 20 characters.