SQL

ลำดับตอนที่ #4 : SQL II - Process Search Results

Processing Results

Omitting Duplicate Data

DISTINCT

By using DISTINCT you can exclude duplicate rows of data from your search results. You can specify the name of a column to get only unique rows, omitting duplicates. To do this, use the following syntax: DISTINCT( column_name )

Using DISTINCT

As shown below, you can use DISTINCT in a SELECT statement to omit duplicate rows. In the example, the statement gets rows of the name column from the purchases table with duplicates excluded. 

Using Arithmetic Operators

Arithmetic Operators

It's possible to do calculations in SQL with the these arithmetic operators: + (addition), - (subtraction), / (division), and * (multiplication). As shown below, using these operators, you can perform calculations on the rows of a specified column.

Using Arithmetic Operators

In order to get the price with tax, we will multiply the price column by 1.09 (for a 9% sales tax rate). Similar to using DISTINCT, arithmetic operators can be used after the SELECT keyword in SQL statements to get the resulting values of a calculation.