How to use distinct in SQL select

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Duplicate values may be included in the table. This is not a problem, but sometimes you may want to list only different (distinct) values. The keyword distinct is used to return a unique different value.

Table A:

Example 1

The copy code is as follows:

Select distinct name from A

The results are as follows:

Example 2

Select distinct name, id from A

The results are as follows:

In fact, it is based on "name+id". Distinct works on both name and id, which is supported by both Access and SQL Server.

Example 3: statistics

Select count (distinct name) from A;-- the number of deduplicated name in the table. SQL Server supports it, but Access does not.

Select count (distinct name, id) from A;-- SQL Server and Access are not supported

Example 4

Select id, distinct name from A;-- will prompt an error because distinct must be placed at the beginning

Other

The fields displayed by select in the distinct statement can only be fields specified by distinct, and other fields are not possible. For example, if Table A has a memo column, it is impossible to get distinc name and the corresponding memo field directly through distinct.

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