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How to use oracle sequence

How to use oracle sequence

Oracle sequences are used to generate unique sequences of numbers, usually used as primary keys or identifiers. Creating a sequence requires specifying the sequence name, starting value, incremental value, maximum value, minimum value, cache size, and loop flags. When using a sequence, use the NEXTVAL keyword to get the next value of the sequence.

Apr 11, 2025 pm 07:36 PM
oracle
How to re-query oracle

How to re-query oracle

Oracle provides multiple deduplication query methods: The DISTINCT keyword returns a unique value for each column. The GROUP BY clause groups the results and returns a non-repetitive value for each group. The UNIQUE keyword is used to create an index containing only unique rows, and querying the index will automatically deduplicate. The ROW_NUMBER() function assigns unique numbers and filters out results that contain only line 1. The MIN() or MAX() function returns non-repetitive values ​​of a numeric column. The INTERSECT operator returns the common values ​​of the two result sets (no duplicates).

Apr 11, 2025 pm 07:33 PM
oracle
How to add table fields to oracle

How to add table fields to oracle

Use the ALTER TABLE statement, the specific syntax is as follows: ALTER TABLE table_name ADD column_name data_type [constraint-clause]. Where: table_name is the table name, column_name is the field name, data_type is the data type, and constraint-clause is an optional constraint. Example: ALTER TABLE employees ADD email VARCHAR2(100) Add an email field to the employees table.

Apr 11, 2025 pm 07:30 PM
oracle
How to use oracle cursor

How to use oracle cursor

Oracle cursor is a database pointer used to traverse a record set, and its features include record-by-record processing, efficiency, updating, and security. Use scenarios include batch processing of data, updating or deleting specific records and transactions.

Apr 11, 2025 pm 07:27 PM
oracle 敏感数据
How to delete the primary key in oracle

How to delete the primary key in oracle

To delete a primary key in Oracle, you need to follow the following steps: 1. Delete the referenced foreign key constraint; 2. Delete the primary key constraint; 3. If necessary, add a new primary key constraint.

Apr 11, 2025 pm 07:24 PM
oracle
How to modify field names of oracle

How to modify field names of oracle

The steps to modify the field name in an Oracle table are as follows: Connect to the database. Use the ALTER TABLE statement to modify the field name. Specify the table name and the old field name. Specify the new field name. Submit changes.

Apr 11, 2025 pm 07:21 PM
oracle
How to configure environment variables in oracle

How to configure environment variables in oracle

Oracle Environment Variable Configuration Guide: Create an ORACLE_HOME environment variable, pointing to the Oracle home directory. Add the Oracle binary directory to the PATH environment variable. Set the TNS_ADMIN environment variable (if the file is named using TNS). Verify the environment variable settings to make sure the output displays the set variables.

Apr 11, 2025 pm 07:18 PM
oracle
How to create primary key constraints in oracle

How to create primary key constraints in oracle

A primary key is a special column or combination of columns that uniquely identifies each row in a table. It ensures that the records in the table are unique and can be created by: Specifying the table name using the ALTER TABLE statement. Add the PRIMARY KEY keyword followed by the column name to specify as the primary key. Primary key constraints help ensure data uniqueness, improve query speeds, prevent duplicate records and simplify table joins.

Apr 11, 2025 pm 07:15 PM
oracle
How to use escaped characters in oracle

How to use escaped characters in oracle

Use escape characters () in Oracle to represent special characters or perform specific actions. Special character escapes include: single quotes ('), double quotes ("), backslash (); operator escapes include: percent sign (%), underscore (_), cap (^), and horn (|). When using escape characters, you need to use them in pairs, and adding spaces before special characters can improve readability.

Apr 11, 2025 pm 07:12 PM
oracle
How to log in with oracle commands

How to log in with oracle commands

To log in to an Oracle database using the command line through the SQLPLUS utility: Open the SQLPLUS utility. Enter your username and password. Use CONNECT / AS SYSDBA to connect to the database. Enter the database password. Verify that the login is successful and the prompt "Connected." is displayed.

Apr 11, 2025 pm 07:09 PM
oracle
How to delete an instance of oracle

How to delete an instance of oracle

To safely delete an Oracle instance, follow these steps: Back up all data. Stop the instance. Disconnect all connections. Uninstall Oracle software. Delete the instance directory. Remove instances from the registry (Windows only).

Apr 11, 2025 pm 07:06 PM
oracle
How to use stored procedures for oracle

How to use stored procedures for oracle

A stored procedure is a set of SQL statements that can be stored in a database and can be called repeatedly as a separate unit. They can accept parameters (IN, OUT, INOUT) and provide the advantages of code reuse, security, performance and modularity. Example: Create a stored procedure calculate_sum to calculate the sum of two numbers and store them in the OUT parameter.

Apr 11, 2025 pm 07:03 PM
oracle 敏感数据
How to deal with oracle garbled code

How to deal with oracle garbled code

Oracle garbled problems are usually caused by improper character set settings. Solutions include: Checking the server, database, and client character sets. Set up the server, database, and client character sets as needed. Use the CONVERT function or the DBMS_LOB.CONVERT_LOB function to fix garbled data. Always specify the character set and set the NLS parameters correctly.

Apr 11, 2025 pm 07:00 PM
oracle
How to modify oracle character set

How to modify oracle character set

To modify the Oracle character set, you need to: back up the database; modify the character set settings in the init.ora file; restart the database; modify existing tables and columns to use the new character set; reload the data; modify the database link (optional).

Apr 11, 2025 pm 06:57 PM
oracle

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