oracle delete sql statement

Oracle database is a commonly used relational database management system that can handle large amounts of transactions and data. When using Oracle database, we often need to delete data. In this case, we need to use Oracle's delete sql statement. This article will introduce you how to use Oracle's delete sql statement.

1. Delete all data

If we want to delete all the data in the database, we can use the following sql statement:

DELETE FROM 表名;

The table name is the table where the data needs to be deleted name.

It should be noted that this statement will delete all data in the table and will not delete the table structure itself. If you want to delete the table structure, you need to use the DROP statement.

2. Delete part of the data

If we only want to delete part of the data in the table, we can use the following sql statement:

DELETE FROM 表名 WHERE 条件;

Among them, the condition is the condition for deleting data, you can Use various operators such as ">", "<", "=", "LIKE", etc.

For example, if we want to delete employees whose salary is less than 5000 in the employee table, we can use the following SQL statement:

DELETE FROM 员工表 WHERE salary<5000;

In this way, all employees whose salary is less than 5000 will be deleted.

It should be noted that if no conditions are specified, all data in the table will be deleted, including the table structure.

3. Delete data in multiple tables

If we want to delete data in multiple tables, we can use the following sql statement:

DELETE FROM 表1,表2 WHERE 表1.字段=表2.字段 AND 条件;

Among them, table 1 and Table 2 is the name of the table where data needs to be deleted, the fields are the field names used to associate the two tables, and the conditions are the conditions for deleting data.

For example, if we want to delete all departments in the employee table and department table where all employees with a salary less than 5,000 are located, we can use the following sql statement:

DELETE FROM 员工表,部门表 WHERE 员工表.dept_id=部门表.dept_id AND 员工表.salary<5000;

In this way, all employees with a salary less than 5,000 The departments to which the employees belong will be deleted.

It should be noted that when deleting data in multiple tables, you need to use join syntax to connect multiple tables.

4. Delete the table

If we want to delete the entire table, we can use the DROP statement:

DROP TABLE 表名;

For example, if we want to delete the employee table, we can use the following statement:

DROP TABLE 员工表;

It should be noted that the DROP statement will delete the table and all its data, so please use it with caution.

The above is an introduction to using Oracle to delete sql statements. In actual database operations, we need to use delete operations with caution, especially deleting tables, to avoid data loss caused by misoperations. At the same time, we should also be clear about the scope and conditions of the data we want to delete to avoid accidentally deleting important data.

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