How to Select the Top 100 Rows In Oracle?

To select the top 100 rows in Oracle, you can use the ROWNUM pseudo-column in combination with the ORDER BY clause. Here is an example query:

1
2
3
4
5
6
7

SELECT *
FROM (
    SELECT *
    FROM your_table
    ORDER BY column_name
)
WHERE ROWNUM <= 100;

In this query, replace your_table with the name of your table and column_name with the column you want to sort the data by. The inner query sorts the rows based on the specified column, and the outer query selects the first 100 rows using the ROWNUM condition. Note that the ROWNUM condition is placed outside the subquery to ensure that the row numbers are generated before applying the filter.

Make sure to adjust the table and column names as per your specific case.

Best Oracle Books to Read in 2024

1

Rating is 5 out of 5

Oracle PL/SQL by Example (The Oracle Press Database and Data Science)

Get Book Now

2

Rating is 4.9 out of 5

Oracle Database 12c DBA Handbook (Oracle Press)

Get Book Now

3

Rating is 4.8 out of 5

Oracle Database Administration: The Essential Refe: A Quick Reference for the Oracle DBA

Get Book Now

4

Rating is 4.7 out of 5

Oracle DBA Mentor: Succeeding as an Oracle Database Administrator

Get Book Now

5

Rating is 4.6 out of 5

OCA Oracle Database SQL Exam Guide (Exam 1Z0-071) (Oracle Press)

Get Book Now

6

Rating is 4.5 out of 5

Oracle Database 12c SQL

Get Book Now

7

Rating is 4.4 out of 5

Oracle Autonomous Database in Enterprise Architecture: Utilize Oracle Cloud Infrastructure Autonomous Databases for better consolidation, automation, and security

Get Book Now

How to select the top 100 rows in MariaDB?

To select the top 100 rows in MariaDB, you can use the LIMIT clause in combination with the SELECT statement. Here is an example:

1
2
3
4

SELECT *
FROM your_table
ORDER BY your_column
LIMIT 100;

Replace your_table with the name of your table and your_column with the column you want to order the results by. This query will retrieve the top 100 rows based on the specified column's sorting order.

What is the difference between TOP and LIMIT in SQL?

In SQL, both TOP and LIMIT are used to limit the number of rows returned in a query result. However, the usage and syntax of these keywords can vary depending on the database management system (DBMS) being used.

1. TOP:

• TOP is mainly used in Microsoft SQL Server, Sybase, and MS Access databases.
• It is placed at the beginning of the SELECT statement followed by the number of records to be fetched.
• The syntax is: SELECT TOP [number] column1, column2 FROM table_name;
• TOP is used to specify the number of rows to be returned from the query result starting from the top.

1. LIMIT:

• LIMIT is primarily used in MySQL and PostgreSQL databases.
• It is placed at the end of the SELECT statement and takes two arguments, starting position (optional) and number of records to be fetched.
• The syntax is: SELECT column1, column2 FROM table_name LIMIT [start], [number];
• LIMIT is used to specify the number of rows to be returned from the query result. It can also be used for pagination by specifying a starting position.

Note: While the functionality is similar, the syntax and usage of TOP and LIMIT may vary between different databases.

How to select the top 100 rows from a join in Oracle?

To select the top 100 rows from a join in Oracle, you can use the ROWNUM pseudocolumn along with the ORDER BY clause. Here's an example:

1
2
3
4
5
6
7
8

SELECT *
FROM (
    SELECT table1.column1, table2.column2
    FROM table1
    JOIN table2 ON table1.column = table2.column
    ORDER BY table1.column1, table2.column2
)
WHERE ROWNUM <= 100;

In the inner query, perform the join and order the result set using the ORDER BY clause. Then, in the outer query, use the ROWNUM pseudocolumn to filter only the top 100 rows.

How to select the top 100 rows based on multiple columns in Oracle?

To select the top 100 rows based on multiple columns in Oracle, you can use the following query:

1
2
3
4
5
6
7

SELECT *
FROM (
    SELECT *
    FROM your_table
    ORDER BY column1, column2, column3
)
WHERE ROWNUM <= 100;

Replace your_table with the actual name of your table and update column1, column2, and column3 with the columns you want to sort by. This query uses a subquery to first order the rows based on the specified columns and then uses the ROWNUM pseudo-column to limit the results to the top 100 rows.

What is the impact of indexes on selecting the top 100 rows in Oracle?

The presence of indexes can have both positive and negative impacts on selecting the top 100 rows in Oracle.

Positive impact:

1. Improved Performance: If there is an index on the column being used for sorting, Oracle can use the index to quickly fetch and order the top 100 rows.
2. Reduced I/O: Using indexes can reduce the number of disk reads required to fetch the data, making the query execution faster.

Negative impact:

1. Increased Cost: If there are multiple indexes on the table, Oracle might need to evaluate the cost of each index to determine the most efficient way to retrieve the data. This evaluation can become costly, especially if the table has a large number of rows or indexes.
2. Extra Steps: Oracle may need to perform additional steps like index scans and sorting, which can slow down the query.

Overall, the impact of indexes on selecting the top 100 rows depends on various factors such as the size of the table, the number of indexes, the selectivity of the query, and the specific configuration of the database. It is recommended to analyze the query execution plans and performance metrics to determine the actual impact of indexes on a specific scenario.