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Simple SELECT Statements in SQL

How to perform simple SELECT statements in SQL (I.e: SQLite or MySQL).

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Edited: 2018-03-27 15:12

SQL SELECT statements

SQL SELECT statements are used to return data from database tables. Most RDBMS uses SQL (Structured Query Language) to allow for easy communication with databases.

A simple SELECT is performed either by choosing which fields you want returned or by using the asterisk (*) wildcard to return everything. Using the asterisk may be fine for testing and niche-situations, but only selecting the fields you actually need will often improve performance.

SELECT * FROM table_name;

Using a WHERE clause allows us to only return specific results:

SELECT * FROM users_table WHERE email= 'peter@example.com';

SQL SELECT statements

To return a specific row, you can use the WHERE clause. Depending on which field you use it on, you might end up selecting a single row or multiple rows. If you use WHERE on a unique field, such as a username, then you should only get a single row.

A SELECT is typically performed by deciding which fields you want returned from the database, this may look like this:

SELECT username, password_hash, email FROM users_table WHERE username = 'Jacob';

If this statement is entered in a command line, you might get a result like:

+----------+---------------+------------------+
| username | password_hash | email            |
+----------+---------------+------------------+
| Jacob    | ...           | blah@example.com |
+----------+---------------+------------------+
1 row in set (0.00 sec)

You can also use asterisk (*) wildcard to select all fields in a database table, this is done like so:

SELECT * FROM table_name;

Performing a wildcard SELECT with a WHERE clause:

SELECT * FROM users_table WHERE username = 'Jacob';