Page 27-Oracle Programming Tutorials: Learn Oracle Online-php.cn

Article Tags

All
web3.0
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Backend Development
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Web Front-end
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Database
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Operation and Maintenance
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Development Tools
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
PHP Framework
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Common Problem
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Other
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Tech
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
CMS Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Java
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
System Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Computer Tutorials
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Hardware Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Mobile Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Software Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Mobile Game Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache

Home

Technical Articles

Database

Oracle

|| usage in oracle

The || operator in Oracle is a logical OR operator used to concatenate Boolean expressions or strings. It returns: Boolean: true if at least one expression is true, false otherwise. String: Concatenates two strings.

May 08, 2024 pm 06:42 PM

oracle

Usage of (+) in oracle

(+) in Oracle represents OUTER JOIN, which is used to merge rows from different tables, even if some rows do not match. Usage: (+) Placed after the forced inclusion row, you can create LEFT, RIGHT or FULL OUTER JOIN. Advantages: Provides a complete data set, including rows with no matching rows; simplifies queries and avoids the use of subqueries or UNIONs.

May 08, 2024 pm 06:39 PM

oracle

What does := mean in Oracle?

Assignment operator in Oracle is := which is used to assign a value to a variable or expression, it creates a new variable or replaces an existing variable and sets it to the value of the expression on the right side of the equal sign.

May 08, 2024 pm 06:36 PM

oracle

drop usage in oracle

The DROP statement is used to delete objects (such as tables, views, indexes) from an Oracle database. It can be used to delete objects that are no longer needed, reorganize the database schema, or free up storage space. The syntax is DROP <object_type> <object_name>;, where <object_type> is the object type and <object_name> is the object name. The CASCADE clause can be used to cascade delete database objects that depend on the object, such as deleting a table and simultaneously deleting its indexes.

May 08, 2024 pm 06:30 PM

oracle

How to use integer in oracle

The INTEGER data type in Oracle is used to store integers between -2,147,483,648 and 2,147,483,647. Mainly used to store integer identifiers, counters and status flags. It should be noted that this data type cannot store decimals or negative numbers, and the storage space is fixed.

May 08, 2024 pm 06:27 PM

oracle

The difference between round and mysqlround in oracle

The Oracle ROUND function returns a NUMBER value, which uses rounding by default and supports rounding to a specified number of decimal places; the MySQL ROUND function returns a DECIMAL value, which adopts double rounding and can only round to an integer.

May 08, 2024 pm 06:24 PM

mysql oracle

How to use insert into select in oracle

The INSERT INTO SELECT statement is used to insert data from one table into another table. It supports inserting all columns or specific columns and can filter using conditions via WHERE clause. Data can be easily transferred from one table to another by specifying the target table, column list, and source table.

May 08, 2024 pm 06:21 PM

oracle

How to get the maximum value of the first piece of data after sorting in Oracle

In Oracle, to get the maximum value of the first piece of data after sorting, you can use the ORDER BY clause and the LIMIT clause: SELECT column_name: Select the column to get the maximum value FROM table_name: Specify the table to get the data ORDER BY column_name DESC: Sort in descending order, ranking the largest value first LIMIT 1: only take the first record, which is the largest value

May 08, 2024 pm 06:18 PM

oracle

What does rowid mean in oracle

ROWID is an identifier that uniquely identifies a row in the Oracle database and consists of file number, area number, block number and slot number. It is used to ensure data integrity, improve query performance, and plays a role in replication and recovery operations. You can obtain the ROWID through the SELECT ROWID statement and use it when updating, deleting, creating an index, or replicating recovery. Note that ROWID is unique within a table but may be the same in different tables and may change when the table structure changes.

May 08, 2024 pm 06:09 PM

oracle 并发访问

What is the difference between rowid and rownum in oracle

ROWID and ROWNUM are used in Oracle to identify rows in a table: ROWID: A unique physical identifier that identifies the row's location on disk and does not change even if the row is updated. ROWNUM: Pseudo column, indicating the row number of the row in the query result set, starting from 1, changing with the order of the rows, and will be reset when the row is added or deleted.

May 08, 2024 pm 06:06 PM

oracle

What is the maximum length of varchar in oracle

The maximum length of a VARCHAR in Oracle depends on the Oracle version and database character set: 4000 bytes for Oracle 11g and earlier, 32767 bytes for Oracle 12c and later. The maximum length is 4000 characters for single-byte character sets (such as ASCII) and 2000 characters for multi-byte character sets (such as UTF-8).

May 08, 2024 pm 06:00 PM

oracle

Which function is used to convert string to date in Oracle?

The function in Oracle that converts a string to the DATE data type is the TO_DATE function. The usage is as follows: TO_DATE(string_expression, format_mask)string_expression: The string value to be converted. format_mask: A mask that specifies the format of the date/time component in a string.

May 08, 2024 pm 05:57 PM

oracle

usage of not in in oracle

The NOT IN operator is used to check if a value is not in the result set of another group or subquery. It is used in the following way: Specify the value to check. Compare the value to a subquery or list of values. Returns all rows where the value is not in the comparison group.

May 07, 2024 pm 04:45 PM

oracle

How to write one or more data files in oracle

The table space of the Oracle database contains one or more data files, which store actual data: Basic files: store actual data Temporary files: store temporary data Rollback segment files: store rollback information Undo segment files: store undo changes to the table Commit changes

May 07, 2024 pm 04:42 PM

oracle