How oracle determines whether a table exists in a stored procedure

Oracle steps to determine whether the table exists in the stored process: 1. Use the "user_tables`" system table to query the table information under the current user, and compare the incoming table name "p_table_name" with the "table_name" field. Compare and meet the conditions, then "COUNT(*)" will return a value greater than 0; 2. Use the "SET SERVEROUTPUT ON;" statement and the "EXEC`" keyword to execute the stored procedure, and pass in the table name to determine the table does it exist.

#The operating environment of this article: Windows 10 system, Oracle version 19c, dell g3 computer.

When developing Oracle database stored procedures, it is sometimes necessary to determine whether a certain table exists in the code so that different logic can be executed based on conditions. This article will introduce how to use PL/SQL code to determine whether a table exists.

Step 1: Use system tables to query whether the table exists

Oracle provides system tables to query object information in the database. We can determine whether a certain object exists by querying these tables. Whether the table exists. The following code demonstrates how to use the system table to query whether a table exists:

CREATEORREPLACEPROCEDUREcheck_table_existence(p_table_nameINVARCHAR2)IS
v_countNUMBER;
BEGIN
SELECTCOUNT(*)INTOv_count
FROMuser_tables
WHEREtable_name=p_table_name;

IFv_count>0THEN
dbms_output.put_line('Table'||p_table_name||'exists!');
ELSE
dbms_output.put_line('Table'||p_table_name||'doesnotexist!');
ENDIF;
EXCEPTION
WHENOTHERSTHEN
dbms_output.put_line('Erroroccurredwhilecheckingtableexistence:'||SQLERRM);
END;

In this stored procedure, we use the `user_tables` system table to query table information under the current user. We compare the incoming table name `p_table_name` with the `table_name` field. If there are records that meet the conditions, `COUNT(*)` will return a value greater than 0.

Step 2: Call the stored procedure for testing

In the created stored procedure, we can call the stored procedure to test the existence of the table. The following code demonstrates how to call a stored procedure:

SETSERVEROUTPUTON;
EXECcheck_table_existence('EMPLOYEES');

In this code, we pass in the table name `EMPLOYEES` to check whether the table exists. After executing the stored procedure, the results will be displayed in the console output.

Code explanation:

- Use the `SET SERVEROUTPUT ON;` statement to turn on PL/SQL output.

- Use the `EXEC` keyword to execute a stored procedure.

- Pass in the table name `EMPLOYEES` as a parameter.

Additional explanation:

- You can call the stored procedure to check the existence of multiple tables, just pass in different table names as parameters in the calling code. Can.

- If you need to query other users' tables, you can use the `ALL_TABLES` and `DBA_TABLES` system tables and modify the query statement as needed.

- In actual applications, different logic can be executed based on the existence of the table, such as creating tables, inserting data, updating tables, etc.

Summary

This article introduces how to determine whether a table exists in an Oracle stored procedure. By querying system tables, we can easily determine whether a certain table exists and write different logic codes based on the results. Please make relevant modifications and optimizations according to actual needs, and confirm the database connection and user permissions before running.

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