How to query the created table in oracle

Oracle is a very popular relational database management system that is widely used in various fields, whether it is business or academic research. In Oracle, we often need to query and manage all database information, such as querying already created data tables. This article will introduce methods of querying tables created in Oracle to help readers better manage their databases.

First of all, in Oracle, we can use the following SQL query statement to query the created table:

SELECT table_name FROM all_tables;

When we run the above SQL statement, Oracle will return all the tables that have been created in the current Information about tables created in the database. Among them, "all_tables" is a predefined view in the Oracle database, which provides us with the metadata information of all tables. However, it should be noted that the results returned by this query do not distinguish the user or group to which the table belongs, so it may include some tables that do not belong to the schema you are currently using.

If you want to query only all tables belonging to the current user, you can use the following SQL query statement:

SELECT table_name FROM user_tables;

In this query, "user_tables" is another predefined view in Oracle , which will return metadata information for all tables of the current user. The results of this query will not include tables belonging to other users, so it is more suitable for managing and querying tables created in the database by the current user.

In addition, if you know the name of the table, you can use the following SQL query to confirm whether the table exists:

SELECT COUNT(*) FROM user_tables WHERE table_name = 'table_name';

The above SQL statement will check whether the table is created by the current user Whether a table named "table_name" exists in the table. The return value is 1 if the table exists, 0 otherwise. This query is often used to ensure that a table has been created to avoid errors in inserting and querying data.

In addition, if you want to query the detailed information of a certain table, you can use the following SQL query statement:

SELECT * FROM user_table_columns WHERE table_name = 'table_name';

This query statement will return the table named "table_name" created by the user. All column information. This query statement is similar to the query method introduced before, but it will return more information, such as the data type of the column, the data length, whether it can be null, and so on. This query statement is very suitable for use when you need to understand the table structure.

To sum up, you can use the following SQL query statement to query tables that have been created in Oracle: SELECT table_name FROM all_tables; SELECT table_name FROM user_tables; SELECT COUNT() FROM user_tables WHERE table_name = ' table_name'; SELECT FROM user_table_columns WHERE table_name = 'table_name';. Readers can use any one or more of these query statements to manage and query their database according to their own needs.

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