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In the previous section, we have
seen that the WHERE keyword
can be used to conditionally
select data from a table. This
condition can be a simple
condition (like the one presented
in the previous section), or it
can be a compound condition.
Compound conditions are made up of
multiple simple conditions
connected by AND
or OR. There is no limit to
the number of simple conditions
that can be present in a single
SQL statement.
The syntax for a
compound condition is as follows:
SELECT
"column_name"
FROM "table_name"
WHERE "simple condition"
{[AND|OR] "simple condition"}+
The {}+ means
that the expression inside the
bracket will occur one or more
times. Note that AND and OR can be
used interchangeably. In addition,
we may use the parenthesis sign () to
indicate the order of the
condition.
For example, we may wish to
select all stores with sales
greater than $1,000 or all stores
with sales less than $500 but
greater than $275 in Table
Store_Information,
Table Store_Information
| store_name |
Sales |
Date |
| Los Angeles |
$1500 |
Jan-05-1999 |
| San Diego |
$250 |
Jan-07-1999 |
| San Francisco |
$300 |
Jan-08-1999 |
| Boston |
$700 |
Jan-08-1999 |
SELECT
store_name
FROM Store_Information
WHERE Sales > 1000
OR (Sales < 500 AND Sales
> 275)
Result:
store_name
Los Angeles
San Francisco
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