Using Top in T-SQL
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A question on using
Top. For example, we have this SQL statement:
SELECT TOP (5) WITH TIES orderid, orderdate, custid, empid FROM Sales.Orders ORDER BY orderdate DESC;
It orders return rows by orderdate first then select the top most five rows.
But isn't that
ORDER clause happens after
SELECT clause, which means that the first five order in random will be returned first then those five rows are ordered by orderdate?
But isn't that
ORDERclause happens after
SELECTclause, which means that the first five order in random will be returned first then those five rows are ordered by orderdate ?
ORDER BY is processed after the
SELECT, but limiting the result set to 5 rows happens even later.
The physical details of actual query processing may vary, but the end result would be as if the server sorted the whole table by
orderdate, then picked the top 5 (or more if needed due to ties) rows, return those rows and discard the rest.
SQL Server SELECT TOP By Practical Examples, 2) Using TOP to return a percentage of rows. The following example uses PERCENT to specify the number of products returned in the result set. The production. sql server - Using Top in T-SQL - Stack Overflow A question on using Top. For example, we have this SQL statement: SELECT TOP (5) WITH TIES orderid, orderdate, custid, empid FROM Sales.Orders ORDER BY orderdate DESC; It orders return rows by
The order of commands in the statement doesn't reflect the actual order of operations that SQL follows. See this article which shows the order to be:
- group by
- order by
As you can see, the TOP operation (limit) is the last to be executed.
SQL SELECT TOP, LIMIT, ROWNUM, select TOP 1 u.ID from except means it first runs the first select, then takes the top 1 result, and finally runs the second and third select to� The SELECT TOP clause is used to specify the number of records to return. The SELECT TOP clause is useful on large tables with thousands of records. Returning a large number of records can impact performance. Note: Not all database systems support the SELECT TOP clause.
Question has already an accepted answer. But I would like to quote content from Microsoft Documentation.
- GROUP BY
- WITH CUBE or WITH ROLLUP
- ORDER BY
T-SQL SELECT TOP 1, This SQL Server tutorial explains how to use the SELECT TOP statement in SQL Server The SQL Server (Transact-SQL) SELECT TOP statement is used to retrieve records from one or more Example - Using TOP PERCENT keyword. The TOP filter is a commonly used construct in T-SQL. Its popularity probably can be attributed to the fact that its design is so well aligned with the way many filtering requirements are expressed—for example, “Return the three most recent orders.”
SQL Server: SELECT TOP Statement, This SQL tutorial explains how to use the SQL SELECT TOP statement with The SQL SELECT TOP statement is used to retrieve records from one or more tables MS Office; Excel � Access � Word Example - Using TOP PERCENT keyword. The SQL TOP clause is used to fetch a TOP N number or X percent records from a table. Note − All the databases do not support the TOP clause. For example MySQL supports the LIMIT clause to fetch limited number of records while Oracle uses the ROWNUM command to fetch a limited number of records.
SQL: SELECT TOP Statement, The TOP filter is a proprietary feature in T-SQL, whereas the OFFSET-FETCH There are two options: using WITH TIES or unique ordering. INSERT TOP n INTO table_name1 (Col1, Col2) SELECT Col3, Col4 FROM table_name2; The tutorial mentions that the TOP here doesn't really achieve anything since the database doesn't have a concept of order, which I kind of get. And is it correct to assume that the n rows that are chosen from table_name2 are completely random records? Example 2:
T-SQL Querying: TOP and OFFSET-FETCH, TOP isn't ANSI compliant and its use manly limited to Microsoft products such as You can replicate the rows returned from TOP using OFFSET and FETCH� The SELECT TOP clause allows you to limit the number of rows or percentage of rows returned in a query result set. Because the order of rows stored in a table is unspecified, the SELECT TOP statement is always used in conjunction with the ORDER BY clause. Therefore, the result set is limited to the first N number of ordered rows.