What is the difference between drop and delete
- 百草Original
- 2023-12-29 11:46:532016browse
The difference between drop and delete: 1. Object; 2. Impact on the database after operation; 3. Syntax; 4. Behavior of occupying resources; 5. Ability to recover data after deletion; 6. Other differences. Detailed introduction: 1. Object, "DELETE" is used to delete records in the table, "DROP" is used to delete the entire table; 2. The impact on the database after the operation, "DELETE" will not change the structure and table definition of the database after execution If there is any impact, after "DROP" is executed, the structure and definition of the entire table will be deleted, etc.
"DROP" and "DELETE" are two commonly used commands in database management. They are in function, purpose, operation object, reversibility, space release, There are clear differences in execution speed and efficiency, interaction with other commands, persistence of effects, syntax and execution, triggers and constraints, and logging.
1. Object:
"DELETE" is used to delete records in the table.
"DROP" is used to delete the entire table.
2. Impact on the database after the operation:
"DELETE" will not have any impact on the structure and table definition of the database after execution.
After "DROP" is executed, the structure and definition of the entire table will be deleted.
3. Syntax:
The syntax of "DELETE" is as follows: DELETE FROM table_name WHERE condition.
The syntax of "DROP" is as follows: DROP TABLE table_name.
4. Behavior of occupying resources:
"DELETE" only deletes the records in the table and does not delete the table itself, so the operation resources are relatively small.
"DROP" deletes the entire table, including table structure and data, so the system resource usage will be higher.
5. Ability to recover data after deletion:
If you accidentally delete your own data, you can use the "UNDELETE" operation to recover the deleted records.
If the entire table is accidentally deleted, the data needs to be restored from backup.
6. Other differences:
"DELETE" is a data manipulation language command, while "DROP" is a data definition language command.
"DELETE" is mainly used to delete data or part of the data and can be rolled back. Delete data in the table based on conditions. If WHERE is not used, all records in the table will be deleted.
"DROP" is mainly used to delete structures (such as databases and tables), including internal data content. For example, to delete a database: DROP DATABASE database name; if you want to delete a column, you also need to use it in ALTER, for example: ALTER TABLE table name DROP column name.
In summary, although "DROP" and "DELETE" are both SQL statements used to delete data, their usage scenarios and functions are different. "DELETE" is used to delete records from the table, while "DROP" is used to delete the entire table. Before using it, developers should know the purpose of their operation and choose the appropriate SQL statement to perform the operation.
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