Distinct Data deduplication Keywords

In the table, duplicate values may be included. That's not a problem, but sometimes you might want to just list different values (distinct). Keyword DISTINCT is used to return only different values.

Table A:

Example 1

Select distinct name from A

The following results are performed:

Example 2

Select DISTINCT name, ID from A

The following results are performed:

is actually based on "Name+id".

Example 3: Statistics

Select COUNT (distinct name) from A;  --The number of the table name to go back to, SQL Server support, and Access does not support select COUNT (distinct name, id) from A;  --sql server and access do not support

Example 4

Select ID, distinct name from A;   --The error will be indicated because the distinct must be placed at the beginning

Other

The field selected in the distinct statement can only be a field specified by distinct, and other fields are not possible. For example, if Table A has a memo column, if you want to get Distinc name and the corresponding Memo field, it is not possible to go directly through distinct.
However, there are other ways to implement a discussion of how SQL Server will stitch up multiple lines of content into one row

Distinct Data deduplication Keywords