Difference between revisions of "SELECT Reference"
From SQLZOO
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SELECT statements may nested - that is the output from one SELECT may be the input to another SELECT. | SELECT statements may nested - that is the output from one SELECT may be the input to another SELECT. | ||
| − | The output from a SELECT may be added to another table using [[INSERT..SELECT]] | + | The output from a SELECT may be added to another table using [[INSERT .. SELECT]] |
Revision as of 10:12, 11 August 2012
SELECT Operations
The SELECT command is used to show data from a database.
The output from a SELECT statement is always a grid - with a number of rows and a number of columns.
Simple SELECT
The simplest SELECT commands involve a single table:
SELECT name, population FROM bbc WHERE region='North America'
| name | population |
|---|---|
| Canada | 32000000 |
| Mexico | 106400000 |
| United States of America | 295000000 |
- The SELECT line determines which columns to show - in this case
nameandpopulation, both of which are columns of the bbc ta le. - The WHERE clause determines which rows to show
The SELECT statement may involve data from more than one table using a JOIN or a UNION.
SELECT statements may nested - that is the output from one SELECT may be the input to another SELECT.
The output from a SELECT may be added to another table using INSERT .. SELECT
