Does distinct preserve order SQL?

Does distinct preserve order SQL?

If you use a DISTINCT , it is logically processed after the SELECT , but the ORDER BY still comes afterwards. So only once the DISTINCT has thrown away the duplicates will the remaining results be put into a particular order – but the rows that have been thrown away can’t be used to determine that order.

What does distinct do in SQL?

The SQL SELECT DISTINCT Statement The SELECT DISTINCT statement is used to return only distinct (different) values. Inside a table, a column often contains many duplicate values; and sometimes you only want to list the different (distinct) values.

How do I select top 5 rows in sql?

SQL SELECT TOP Clause

1. SQL Server / MS Access Syntax. SELECT TOP number|percent column_name(s) FROM table_name;
2. MySQL Syntax. SELECT column_name(s) FROM table_name. LIMIT number;
3. Example. SELECT * FROM Persons. LIMIT 5;
4. Oracle Syntax. SELECT column_name(s) FROM table_name. WHERE ROWNUM <= number;
5. Example. SELECT * FROM Persons.

How to select only unique Rows in SQL?

The SQL Distinct command can be used in the SELECT statement to ensure that the query returns only distinct (unique) rows. When the query is selecting the rows it discards any row which is a duplicate of any other row already selected by the query. The syntax for DISTINCT is as follows: SELECT DISTINCT [ ColumnName,..]

When to use distinct to return only unique Rows?

Using SQL DISTINCT The SQL Distinct command can be used in the SELECT statement to ensure that the query returns only distinct (unique) rows. When the query is selecting the rows it discards any row which is a duplicate of any other row already selected by the query. The syntax for DISTINCT is as follows:

When to use distinct in the SELECT statement?

The SQL Distinct command can be used in the SELECT statement to ensure that the query returns only distinct (unique) rows. When the query is selecting the rows it discards any row which is a duplicate of any other row already selected by the query. The syntax for DISTINCT is as follows:

How can I select rows with most recent timestamp for each?

I have a table of sensor data. Each row has a sensor id, a timestamp, and other fields. I want to select a single row with latest timestamp for each sensor, including some of the other fields. I thought that the solution would be to group by sensor id and then order by max (timestamp) like so: