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.

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.

Navicat for MariaDB cannot view the database password directly because the password is stored in encrypted form. To ensure the database security, there are three ways to reset your password: reset your password through Navicat and set a complex password. View the configuration file (not recommended, high risk). Use system command line tools (not recommended, you need to be proficient in command line tools).

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.

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.

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.

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()).

Recovering deleted rows directly from the database is usually impossible unless there is a backup or transaction rollback mechanism. Key point: Transaction rollback: Execute ROLLBACK before the transaction is committed to recover data. Backup: Regular backup of the database can be used to quickly restore data. Database snapshot: You can create a read-only copy of the database and restore the data after the data is deleted accidentally. Use DELETE statement with caution: Check the conditions carefully to avoid accidentally deleting data. Use the WHERE clause: explicitly specify the data to be deleted. Use the test environment: Test before performing a DELETE operation.