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Explanation of Retrieving Columns of Data from a Database Table - Succeed in Using SQL. Also refer to Structured Query Language, Access, MySQL, MS SQL Server, SELECT, wildcard, comma, Ron Kurtus, School for Champions. Copyright © Restrictions
Retrieving Columns of Data from a Database Table in SQL
by Ron Kurtus (3 February 2007)
You can use SQL to retrieve the columns of a database table with the SELECT statement. You can retrieve all columns, a single column, or several specific columns. It is then up to your programming language to display that data.
Questions you may have include:
- How do you retrieve all columns?
- How do you retrieve a single columns?
- How do you retrieve selected columns?
This lesson will answer those questions. There is a mini-quiz near the end of the lesson.
Retrieve all columns
You can query a database to retrieve all the elements in a database table by using the SELECT statement and wildcard (*) indicator.
SELECT *
FROM table_name;Note: It is standard practice to add ";" at the end of your SQL query. Some databases require it and some don't.
Retrieve single column
The most common query from a database is to collect or retrieve all the elements in a specific column of the database table.
SELECT column_name
FROM table_name;
Retrieve several select columns
You can also retrieve data from several columns by separating the column names with a comma.
SELECT column_1, column_2, column_7
FROM table_name;Note: Do not place a comma after the last item in the list, because it will result in an error message.
Summary
The SELECT statement is used to retrieve the columns of a database table. You can retrieve all columns, a single column, or several specific columns.
Always do your best
Resources
The following are resources on this subject.
Websites
Books
Mini-quiz to check your understanding
If you got all three correct, you are on your way to becoming a Champion in working with SQL. If you had problems, you had better look over the material again.
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Retrieving Columnsof Data from a Database Table in SQL