How to query data size through various tools in Oracle

Oracle is a well-known relational database management system through which rich data can be stored and managed. When using Oracle database, sometimes you need to query the data size of a certain table or column in order to optimize or plan the data storage space. This article will introduce how to query the data size through various tools in Oracle.

1. Query through SQL statements

1.1. Query the size of the table

To query the size of a certain table, you can use the following SQL statement:

SELECT segment_name, bytes/1024/1024 MB
FROM user_segments
WHERE segment_type = 'TABLE'
AND segment_name = '表名';

Among them , segment_name represents the table name, BYTES represents the size of the table space in bytes, and MB represents conversion to megabytes. By dividing BYTES by 1024 and then dividing by 1024, you can get the size of the table.

1.2. Query the size of a column

To query the size of a column, you can use the following SQL statement:

SELECT column_name, data_type, data_length/1024/1024 MB
FROM user_tab_columns
WHERE table_name = '表名'
AND column_name = '列名';

Among them, column_name represents the column name, DATA_TYPE represents the data type, and DATA_LENGTH Indicates the data length in bytes.

2. Query through Oracle Enterprise Manager

Oracle Enterprise Manager is a tool for managing Oracle databases, through which you can query the size of the database.

2.1. Query the size of the table

In the Oracle Enterprise Manager interface, you can query the size of the table through the following steps:

Select "Table Space" → "Table" → "View Table" → You can see the size of the table in the "Statistics" tab.

2.2. Query the size of a column

In the Oracle Enterprise Manager interface, you can query the size of a column through the following steps:

Select "Table Space" → "Table ” → “View Table” → You can see the size of the columns in the “Columns” tab.

3. Query through the command line

When using the command line to query the size of the Oracle database, you need to use the tools provided by Oracle, such as SQLPLUS and SQL*Loader. The following are the steps to query the database size:

3.1. Log in to SQLPLUS

After logging in to SQLPLUS, you can use the following command to query the size of the database:

SELECT tablespace_name, SUM(bytes)/1024/1024/1024 "Size(GB)"
FROM dba_data_files
GROUP BY tablespace_name;

Among them, TABLESPACE_NAME represents the table space , BYTES represents the size of the space, the unit is bytes, Size (GB) represents the size converted into gigabytes.

3.2. Log in to SQL * Loader

After logging in to SQL * Loader, you can use the following command to query the size of the table or column:

SELECT column_name, data_type, data_length/1024/1024 mb
FROM user_tab_columns
WHERE table_name='TABLE_NAME';

Among them, COLUMN_NAME represents the column name and DATA_TYPE Indicates the data type, DATA_LENGTH indicates the data length in bytes, and MB indicates conversion to megabytes.

In summary, there are many ways to query data size in Oracle, which can be achieved through SQL statements, Oracle Enterprise Manager, command line and other tools. Choose the appropriate method for querying based on actual needs.

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