Three ways to query foreign keys in Oracle tables

In Oracle database, the relationship between tables can be realized using foreign keys. Foreign key is a strong constraint, which can ensure the integrity of data and improve the efficiency of data query. When we want to query the foreign keys of a table, we can use a variety of methods. This article will introduce some of the more commonly used methods.

Method 1: Query the system table

In the Oracle database, the system table USER_CONSTRAINTS can list all constraints. We can use the following statement to query all foreign keys of a table:

SELECT a.table_name,

a.constraint_name,

b.column_name,

a.r_constraint_name,

a.delete_rule

FROM user_constraints a,

user_cons_columns b

WHERE a.constraint_type = 'R'

AND a.constraint_name = b.constraint_name

AND a.table_name = 'your_table_name';

Among them, a.table_name refers to the name of the table we want to query the foreign key. The query results will return the name, corresponding column, reference table and deletion rule of each foreign key.

Method 2: Use Oracle SQL Developer

Oracle SQL Developer is a free client tool. It has a more friendly user interface than other tools and can help us easily query the relationships between tables. . We can query all foreign keys of a table through the following steps:

1. Open Oracle SQL Developer and connect to the corresponding database.
2. Select the required table under the Connections panel.
3. Select the "Constraints" tab in the Properties window on the right.
4. In the "Foreign Key Constraints" area, you can view all foreign keys and reference tables of the table.

Method 3: Query the data dictionary

Oracle database has its own data dictionary, which can be used to store relevant information of system tables. We can query all foreign keys of a table through the following statement:

SELECT a.table_name,

a.constraint_name,

b.column_name,

a.r_constraint_name,

a.delete_rule

FROM user_constraints a,

user_cons_columns b

WHERE a.constraint_type = 'R'

AND a.constraint_name = b.constraint_name

AND a.table_name = 'your_table_name';

Among them, a.table_name refers to the name of the table we want to query the foreign key. The query results will return the name, corresponding column, reference table and deletion rule of each foreign key.

Summary

The above introduces three methods of querying foreign keys of Oracle database tables, among which the method of querying system tables and data dictionary is the most commonly used and traditional method. Using Oracle SQL Developer is a more intuitive and faster method. No matter which method is used, the queried information should be analyzed and compared to ensure the integrity and correctness of the data.

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