Database
Mysql Tutorial
How Can I Concatenate Multiple Rows into a Single Row in Oracle Without Using a Stored Procedure?
How Can I Concatenate Multiple Rows into a Single Row in Oracle Without Using a Stored Procedure?
Concatenating Multiple Rows into a Single Row in Oracle Without a Stored Procedure
When working with data in Oracle, there may be instances where you need to combine multiple rows into a single row. Traditionally, this could be achieved using a stored procedure. However, there is a more efficient and straightforward solution using Oracle's LISTAGG clause.
The LISTAGG Clause in Oracle
Introduced in Oracle 11gR2, the LISTAGG clause allows you to concatenate multiple values into a single string. It takes the following syntax:
LISTAGG(expression, delimiter) WITHIN GROUP (ORDER BY column)
- expression: The column or expression you want to concatenate.
- delimiter: The separator you want to use between the values (e.g., a comma).
- column: The column used to order the values within each group.
Example
Consider the following data set:
| question_id | element_id |
|---|---|
| 1 | 7 |
| 1 | 8 |
| 2 | 9 |
| 3 | 10 |
| 3 | 11 |
| 3 | 12 |
To concatenate the element_id values for each question_id into a single row, we can use the following query:
SELECT question_id,
LISTAGG(element_id, ',') WITHIN GROUP (ORDER BY element_id)
FROM your_table
GROUP BY question_id;
Output
| question_id | element_id |
|---|---|
| 1 | 7,8 |
| 2 | 9 |
| 3 | 10,11,12 |
Considerations for Large Result Strings
If the resulting string is expected to exceed 4000 characters (the maximum length for a VARCHAR2 data type), you can use the following enhancement introduced in Oracle 12cR2:
SELECT question_id,
LISTAGG(element_id, ',') WITHIN GROUP (ORDER BY element_id) ON OVERFLOW TRUNCATE/ERROR
FROM your_table
GROUP BY question_id;
- ON OVERFLOW TRUNCATE: Truncates the result string if it exceeds the specified length.
- ON OVERFLOW ERROR: Raises an error if the result string exceeds the specified length.
The above is the detailed content of How Can I Concatenate Multiple Rows into a Single Row in Oracle Without Using a Stored Procedure?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
1793
16
1736
56
1588
29
267
587
Establishing secure remote connections to a MySQL server
Jul 04, 2025 am 01:44 AM
TosecurelyconnecttoaremoteMySQLserver,useSSHtunneling,configureMySQLforremoteaccess,setfirewallrules,andconsiderSSLencryption.First,establishanSSHtunnelwithssh-L3307:localhost:3306user@remote-server-Nandconnectviamysql-h127.0.0.1-P3307.Second,editMyS
How to add the MySQL bin directory to the system PATH
Jul 01, 2025 am 01:39 AM
To add MySQL's bin directory to the system PATH, it needs to be configured according to the different operating systems. 1. Windows system: Find the bin folder in the MySQL installation directory (the default path is usually C:\ProgramFiles\MySQL\MySQLServerX.X\bin), right-click "This Computer" → "Properties" → "Advanced System Settings" → "Environment Variables", select Path in "System Variables" and edit it, add the MySQLbin path, save it and restart the command prompt and enter mysql--version verification; 2.macOS and Linux systems: Bash users edit ~/.bashrc or ~/.bash_
Where does mysql workbench save connection information
Jun 26, 2025 am 05:23 AM
MySQLWorkbench stores connection information in the system configuration file. The specific path varies according to the operating system: 1. It is located in %APPDATA%\MySQL\Workbench\connections.xml in Windows system; 2. It is located in ~/Library/ApplicationSupport/MySQL/Workbench/connections.xml in macOS system; 3. It is usually located in ~/.mysql/workbench/connections.xml in Linux system or ~/.local/share/data/MySQL/Wor
Analyzing the MySQL Slow Query Log to Find Performance Bottlenecks
Jul 04, 2025 am 02:46 AM
Turn on MySQL slow query logs and analyze locationable performance issues. 1. Edit the configuration file or dynamically set slow_query_log and long_query_time; 2. The log contains key fields such as Query_time, Lock_time, Rows_examined to assist in judging efficiency bottlenecks; 3. Use mysqldumpslow or pt-query-digest tools to efficiently analyze logs; 4. Optimization suggestions include adding indexes, avoiding SELECT*, splitting complex queries, etc. For example, adding an index to user_id can significantly reduce the number of scanned rows and improve query efficiency.
Performing logical backups using mysqldump in MySQL
Jul 06, 2025 am 02:55 AM
mysqldump is a common tool for performing logical backups of MySQL databases. It generates SQL files containing CREATE and INSERT statements to rebuild the database. 1. It does not back up the original file, but converts the database structure and content into portable SQL commands; 2. It is suitable for small databases or selective recovery, and is not suitable for fast recovery of TB-level data; 3. Common options include --single-transaction, --databases, --all-databases, --routines, etc.; 4. Use mysql command to import during recovery, and can turn off foreign key checks to improve speed; 5. It is recommended to test backup regularly, use compression, and automatic adjustment.
Handling NULL Values in MySQL Columns and Queries
Jul 05, 2025 am 02:46 AM
When handling NULL values in MySQL, please note: 1. When designing the table, the key fields are set to NOTNULL, and optional fields are allowed NULL; 2. ISNULL or ISNOTNULL must be used with = or !=; 3. IFNULL or COALESCE functions can be used to replace the display default values; 4. Be cautious when using NULL values directly when inserting or updating, and pay attention to the data source and ORM framework processing methods. NULL represents an unknown value and does not equal any value, including itself. Therefore, be careful when querying, counting, and connecting tables to avoid missing data or logical errors. Rational use of functions and constraints can effectively reduce interference caused by NULL.
Resetting the root password for MySQL server
Jul 03, 2025 am 02:32 AM
To reset the root password of MySQL, please follow the following steps: 1. Stop the MySQL server, use sudosystemctlstopmysql or sudosystemctlstopmysqld; 2. Start MySQL in --skip-grant-tables mode, execute sudomysqld-skip-grant-tables&; 3. Log in to MySQL and execute the corresponding SQL command to modify the password according to the version, such as FLUSHPRIVILEGES;ALTERUSER'root'@'localhost'IDENTIFIEDBY'your_new
how to check mysql version on windows command prompt
Jul 01, 2025 am 01:41 AM
To check the MySQL version, you can use the following methods in the Windows command prompt: 1. Use the command line to view directly, enter mysql--version or mysql-V; 2. After logging in to the MySQL client, execute SELECTVERSION();; 3. Manually search through the installation path, switch to the MySQL bin directory and run mysql.exe--version. These methods are suitable for different scenarios, the first two are most commonly used, and the third one is suitable for situations where environment variables are not configured.
