Oracle DB 使用转换函数和条件表达式
CASE表达式使你可以在SQL 语句中使用IF-THEN-ELSE逻辑，而无需调用任何过程。在简单的CASE表达式中，Oracle Server 会搜索其expr
以下代码是一个搜索CASE表达式示例。在搜索CASE表达式中，搜索从左到右进行，直到找到列出的条件，，然后它会返回相应的返回表达式。如果找不到满足的条件，但存在一个ELSE子句，则返回ELSE子句中的返回表达式，其它情况则返回NULL。
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
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
1377
52
How to check tablespace size of oracle
Apr 11, 2025 pm 08:15 PM
To query the Oracle tablespace size, follow the following steps: Determine the tablespace name by running the query: SELECT tablespace_name FROM dba_tablespaces; Query the tablespace size by running the query: SELECT sum(bytes) AS total_size, sum(bytes_free) AS available_space, sum(bytes) - sum(bytes_free) AS used_space FROM dba_data_files WHERE tablespace_
How to import oracle database
Apr 11, 2025 pm 08:06 PM
Data import method: 1. Use the SQLLoader utility: prepare data files, create control files, and run SQLLoader; 2. Use the IMP/EXP tool: export data, import data. Tip: 1. Recommended SQL*Loader for big data sets; 2. The target table should exist and the column definition matches; 3. After importing, data integrity needs to be verified.
How to uninstall Oracle installation failed
Apr 11, 2025 pm 08:24 PM
Uninstall method for Oracle installation failure: Close Oracle service, delete Oracle program files and registry keys, uninstall Oracle environment variables, and restart the computer. If the uninstall fails, you can uninstall manually using the Oracle Universal Uninstall Tool.
How to create a table in oracle
Apr 11, 2025 pm 08:00 PM
Creating an Oracle table involves the following steps: Use the CREATE TABLE syntax to specify table names, column names, data types, constraints, and default values. The table name should be concise and descriptive, and should not exceed 30 characters. The column name should be descriptive, and the data type specifies the data type stored in the column. The NOT NULL constraint ensures that null values are not allowed in the column, and the DEFAULT clause specifies the default values for the column. PRIMARY KEY Constraints to identify the unique record of the table. FOREIGN KEY constraint specifies that the column in the table refers to the primary key in another table. See the creation of the sample table students, which contains primary keys, unique constraints, and default values.
How to view instance name of oracle
Apr 11, 2025 pm 08:18 PM
There are three ways to view instance names in Oracle: use the "sqlplus" and "select instance_name from v$instance;" commands on the command line. Use the "show instance_name;" command in SQL*Plus. Check environment variables (ORACLE_SID on Linux) through the operating system's Task Manager, Oracle Enterprise Manager, or through the operating system.
How to re-query oracle
Apr 11, 2025 pm 07:33 PM
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).
How to encrypt oracle view
Apr 11, 2025 pm 08:30 PM
Oracle View Encryption allows you to encrypt data in the view, thereby enhancing the security of sensitive information. The steps include: 1) creating the master encryption key (MEk); 2) creating an encrypted view, specifying the view and MEk to be encrypted; 3) authorizing users to access the encrypted view. How encrypted views work: When a user querys for an encrypted view, Oracle uses MEk to decrypt data, ensuring that only authorized users can access readable data.
How to read the oracle awr report
Apr 11, 2025 pm 09:45 PM
An AWR report is a report that displays database performance and activity snapshots. The interpretation steps include: identifying the date and time of the activity snapshot. View an overview of activities and resource consumption. Analyze session activities to find session types, resource consumption, and waiting events. Find potential performance bottlenecks such as slow SQL statements, resource contention, and I/O issues. View waiting events, identify and resolve them for performance. Analyze latch and memory usage patterns to identify memory issues that are causing performance issues.
