How to add multiple new columns in SQL

The DATETIME data type is used to store high-precision date and time information, ranging from 0001-01-01 00:00:00 to 9999-12-31 23:59:59.99999999, and the syntax is DATETIME(precision), where precision specifies the accuracy after the decimal point (0-7), and the default is 3. It supports sorting, calculation, and time zone conversion functions, but needs to be aware of potential issues when converting precision, range and time zones.

To create an Oracle database, the common method is to use the dbca graphical tool. The steps are as follows: 1. Use the dbca tool to set the dbName to specify the database name; 2. Set sysPassword and systemPassword to strong passwords; 3. Set characterSet and nationalCharacterSet to AL32UTF8; 4. Set memorySize and tablespaceSize to adjust according to actual needs; 5. Specify the logFile path. Advanced methods are created manually using SQL commands, but are more complex and prone to errors. Pay attention to password strength, character set selection, tablespace size and memory

Use the DELETE statement to delete data from the database and specify the deletion criteria through the WHERE clause. Example syntax: DELETE FROM table_name WHERE condition; Note: Back up data before performing a DELETE operation, verify statements in the test environment, use the LIMIT clause to limit the number of deleted rows, carefully check the WHERE clause to avoid misdeletion, and use indexes to optimize the deletion efficiency of large tables.

PostgreSQL The method to add columns is to use the ALTER TABLE command and consider the following details: Data type: Select the type that is suitable for the new column to store data, such as INT or VARCHAR. Default: Specify the default value of the new column through the DEFAULT keyword, avoiding the value of NULL. Constraints: Add NOT NULL, UNIQUE, or CHECK constraints as needed. Concurrent operations: Use transactions or other concurrency control mechanisms to handle lock conflicts when adding columns.

Navicat itself does not store the database password, and can only retrieve the encrypted password. Solution: 1. Check the password manager; 2. Check Navicat's "Remember Password" function; 3. Reset the database password; 4. Contact the database administrator.

How to choose Oracle 11g migration tool? Determine the migration target and determine the tool requirements. Mainstream tool classification: Oracle's own tools (expdp/impdp) third-party tools (GoldenGate, DataStage) cloud platform services (such as AWS, Azure) to select tools that are suitable for project size and complexity. FAQs and Debugging: Network Problems Permissions Data Consistency Issues Insufficient Space Optimization and Best Practices: Parallel Processing Data Compression Incremental Migration Test

It is impossible to view PostgreSQL passwords directly from Navicat, because Navicat stores passwords encrypted for security reasons. To confirm the password, try to connect to the database; to modify the password, please use the graphical interface of psql or Navicat; for other purposes, you need to configure connection parameters in the code to avoid hard-coded passwords. To enhance security, it is recommended to use strong passwords, periodic modifications and enable multi-factor authentication.

How to clean all Redis data: Redis 2.8 and later: The FLUSHALL command deletes all key-value pairs. Redis 2.6 and earlier: Use the DEL command to delete keys one by one or use the Redis client to delete methods. Alternative: Restart the Redis service (use with caution), or use the Redis client (such as flushall() or flushdb()).