What function is used to define a certain character in Oracle?

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_

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.

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.

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.

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.

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.

There are the following methods to get time in Oracle: CURRENT_TIMESTAMP: Returns the current system time, accurate to seconds. SYSTIMESTAMP: More accurate than CURRENT_TIMESTAMP, to nanoseconds. SYSDATE: Returns the current system date, excluding the time part. TO_CHAR(SYSDATE, 'YYY-MM-DD HH24:MI:SS'): Converts the current system date and time to a specific format. EXTRACT: Extracts a specific part from a time value, such as a year, month, or hour.

To create a user in Oracle, follow these steps: Create a new user using the CREATE USER statement. Grant the necessary permissions using the GRANT statement. Optional: Use the RESOURCE statement to set the quota. Configure other options such as default roles and temporary tablespaces.