{"id":1276,"date":"2025-04-06T16:49:58","date_gmt":"2025-04-06T16:49:58","guid":{"rendered":"https:\/\/learnlearn.uk\/ibcs\/?page_id=1276"},"modified":"2025-04-06T16:49:58","modified_gmt":"2025-04-06T16:49:58","slug":"select-queries","status":"publish","type":"page","link":"https:\/\/learnlearn.uk\/ibcs\/select-queries\/","title":{"rendered":"SELECT Queries"},"content":{"rendered":"
\n

Intro<\/h2>\n
\n\n

SQL Queries<\/h2>\n

A query is a request for data or information from a database table or combination of tables. This query can be thought of as providing a “view” of the database, which means it presents a specific slice or interpretation of the database data according to the query’s conditions and structure.<\/p>\n

Queries that view the database contents use the SELECT keyword<\/p>\n\n<\/div>

SELECT<\/h2>\n
\n\n

SELECT Query<\/h2>\n

The simplest form of SELECT query uses the * wildcard operator to retrieve all database columns from the table.<\/p>\n

Here’s a basic SQL SELECT query that retrieves all columns for all customers in the Customers table:<\/p>\n

SELECT * FROM Customers;<\/pre>\n
If you only want to retrieve data from certain columns then you can specific the column data the you wish to retrieve:<\/p>\n
SELECT CustomerName, EmailAddress FROM Customers;<\/pre>\n
<\/div>\n\n<\/div>
WHERE<\/h2>\n
\n\n
Filtering using WHERE<\/h2>\n
Queries can filter data based on specific criteria, showing only the data that meets these conditions.<\/p>\n
SELECT name, department, salary\u00a0\r\nFROM employees\u00a0\r\nWHERE department = 'Marketing'<\/pre>\n
This query selects employees in the Marketing department.<\/p>\n\n<\/div>
ORDER BY<\/h2>\n
\n\n
ORDER BY Clause<\/h2>\n
The ORDER BY clause in SQL is used to sort the result set of a query by one or more columns. It can sort the data in ascending order (which is the default) or descending order, based on the specified column(s).<\/p>\n
Example: Employees Table<\/h4>\n
If you want to retrieve all employees’ first and last names, sorted by the LastName in ascending order and then by FirstName in descending order, your query would look like this:<\/p>\n
SELECT FirstName, LastName\r\nFROM Employees\r\nORDER BY LastName ASC, FirstName DESC;<\/pre>\n\n<\/div>
LIKE<\/h2>\n
\n\n
LIKE Operator<\/h2>\n
The LIKE operator in SQL is used in a WHERE clause to search for a specified pattern in a column. It’s particularly useful when you want to perform searches on strings, such as finding rows with columns that contain a certain substring, begin with specific characters, or end with specific characters. The % and _ are two wildcards often used with LIKE:<\/p>\n