从列中选择唯一条目

Question

I have this table ID | Category | Subcategory |

           1  |      Books       |    Comic         |
           2  |      Books       |   Fiction        |
           3  |      Cars        |     New          |
           4  |      Books       |   Non- fiction   |
           4  |      Cars        |    Second hand   |

and I want to select only unique entries from the column 'Category'. That is, I want 'Books' and 'Cars' to be selected only once. How can I write a query ?? Help please.

Answer 1

You mean distinct ?

SELECT Distinct Category
FROM Table

Answer 2

Or group by

SELECT Category
FROM Table
GROUP BY Category

Group by enables you to retrieve various aggregates based on your query (such as number of items in category etc...)