Use of the Union and Union ALL of SQL statements _mssql

The Union and JOIN statements in SQL are very similar, but the union has a constraint: two SQL statements produce a field that needs to be the same type of data, and the final result will see a different data value.

Format:

[SQL Statement 1]
UNION
[SQL Statement 2]

For example:

Table Store_info

and table Internet_sales

Use the Union statement:

Copy Code code as follows:

SELECT Date from Store_info
UNION
SELECT Date from Internet_sales

Results:

Or:

Copy Code code as follows:

SELECT Date,sales from Store_info
UNION
SELECT Date,sales from Internet_sales

Results:

Finally, the union all and the Union are basically the same, except that the result is that it contains duplicate data.

Such as:

Copy Code code as follows:

SELECT Date from Store_info
UNION All
SELECT Date from Internet_sales

Results:

The above is the SQL statement of the Union and the use of union all the content, I hope to give you a reference, but also hope that we support the cloud habitat community.