SQL is a standard language for storing, manipulating and retrieving data in databases. Our SQL tutorial will teach you how to use SQL in: MySQL, SQL Server, MS Access, Oracle, Sybase, Informix, …

In this tutorial we will use the well-known Northwind sample database (included in MS Access and MS SQL Server). Below is a selection from the Customers table used in the examples:

RDBMS is the basis for SQL, and for all modern database systems such as MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access. The data in RDBMS is stored in database objects called tables.

Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, Python, PHP, Bootstrap, Java, XML and more.

Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, Python, PHP, Bootstrap, Java, XML and more.

In the previous chapter we learned how to connect to the database using the SQL Shell (psql) application, which is a command-based application that allows us to interact with the PostgreSQL …

Once you have connected to the database, you can start executing SQL statements. Our database is empty, so we cannot query any tables yet, but we can check the version with this SQL statement:

Database Queries A query is a question or a request. We can query a database for specific information and have a recordset returned. Look at the following query (using standard SQL):

First, we set up an SQL query that selects the id, firstname and lastname columns from the MyGuests table. The next line of code, $conn->query($sql), runs the query and puts the resulting data into a …

The SQL WHERE Clause The WHERE clause is used to filter records. It is used to extract only those records that fulfill a specified condition.