1. When creating a user with CREATE USER, a schema corresponding to that user name is automatically created.
2. To execute CREATE USER, you need the CREATEROLE authority, or the appropriate authority equal to or greater than it.
3. Deleting a user with DROP USER deletes objects owned by the user at the same time.
4. To execute DROP USER, DROPROLE authority or appropriate authority equivalent to or higher than DROPROLE authority is required.
5. You can change the user's name with ALTER USER.

1. Obtain the table lock of the target table and retrieve unnecessary areas in the table.
2. Automatic vacuum can be executed by executing VACUUM AUTO ON.
3. By executing VACUUM DETAILS, details of the execution status of VACUUM are output.
4. When VACUUM ANALYZE is executed, the statistical information of the table is acquired.
5. When VACUUM FULL is executed, all the tables in the database are subjected to VACUUM.

1. Only the user who owns the table (that is, the person who executed  CREATE TABLE) has access to the table immediately after its creation. 

2. Only the owner of the table can grant the table access rights to the user.

3. The owner of the table can grant or deny each user the authority to create a view based on that table.
4. Despite being the owner of the table, there is no access right to the table and SELECT can not be executed.

1. It can be created from the psql command by executing the CREATE CLUSTER statement.
2. It can be created by executing the initdb command from the OS command prompt.
3. You can create it by executing the pg_ctl initdb command from the OS command prompt.
4. For security reasons, files to be created are not permitted to be read except by the user who executed the command.
5. For security reasons, OS administrator user (root on Linux) should create it.

1. Use createuser to create users and createrole commands to create roles.
2. To execute the createuser command, you need the CREATEUSER privilege.
3. Executing with the -d option grants database creation authority to new users.
4. When executed with the -u option, new user is granted user creation authority.

5. When executed with the -s option, the superuser privilege is granted to the new user.

1.  port 
2. max_connections 
3. log_connections
4. log_line_ prefix
5. search_path

1. For security reasons, password entry is mandatory regardless of the type of authentication method you have specified.
2. Instead of storing the password in the database body, you can use an external server such as LDAP.
3. In order to connect to the database, the user name must be registered in pg_hba.conf.
4. It is possible to specify different authentication methods depending on the network and host of the connection source.
5. When the authentication method is not specified, password authentication is done by default.

1. Database superuser privilege is required to execute pg_dump.
2. You can back up not only data of tables but also data of users and roles created with CREATE USER or CREATE ROLE.
3. In addition to table data, you can also back up access privileges to tables granted / deprived by GRANT or REVOKE.
4. You can back up only table definitions such as CREATE TABLE without dumping data.
5. When backing up in binary format, restoring data is restricted to servers of the same architecture.

1. Use OS commands such as tar to copy files.
2. Use the PostgreSQL pg_backup command to copy files.
3. When copying a file, the database must be stopped.
4. You copy only the files under the directory of the database cluster.
5. Generally, backups by file copy are smaller in size than logical backup by pg_dump.

1. Execute the pg_dumpall command.
2. Execute the pg_basebackup command.
3. Stop the database with pg_ctl stop, then create a physical copy of the database cluster with the tar command.

4. Connect to database as administrator user in psql, select pg_start_backup ('label');

   After that, make a physical copy of the database cluster with the tar command.

5. Connect to the database as an administrator user with psql and execute select pg_create_backup ('backup_file');

In order to execute the COPY statement, the database administrator authority is required.

1. It is defined in standard SQL and can be used with many RDBMS, including PostgreSQL.
2. The \copy meta command of psql internally executes the SQL COPY statement.
3. In order to execute the COPY statement, the database administrator authority is required.
4. Input and output files of CSV (Comma Separated Values) format by default.
5. When restoring from a text format backed up by using pg_dump command, the COPY statement is used by default.

1. Whether the user has superuser privileges
2. Whether the user has the authority to newly create a user
3. Whether the user has the authority to create a new table newly
4. User's name
5. User's password

1. Because all data in a table is analyzed, it takes time for large tables.
2. Since an exclusive lock on the table is required, it is not possible to access the data during execution of vacuum.
3. It can be executed by either the ANALYZE command or the VACUUM command.
4. Generally, it is sufficient to execute only once for each table.
5. By optional specification, it can be applied to either  all tables in the database, only specific tables in the database, or only certain columns of a specific table.

1. Automatic vacuum is started regularly and vacuum processing is executed for all tables in the database.
2. Although it is possible to operate the database without executing automatic vacuum, it is strongly  recommended to execute it.
3. When setting to execute automatic vacuum, it is better not to perform manual vacuum processing.
4. Automatic vacuum is activated only when the load on the database is relatively small.
5. Automatic vacuum automatically not only vacuum (VACUUM) but also ANALYZE processing

1. When SELECT current_user; is executed, a list of user names currently connected to the database are displayed.
2. When SELECT current_user; is executed, the user name of the user who executed this SELECT statement is displayed.
3. SELECT current_user ('bob'); allows you to change the user who is running the session.
4. You can use UPDATE current_user = 'bob'; to change the user running the session.
5. An error will occur if you add parentheses, such as SELECT current_user ();. 

1. Available for all relational databases, including PostgreSQL.
2. The specification is part of the ANSI SQL standards.

3. Holds various information about objects in the database.

4. It is defined as a view in the schema named information.

5. Content is equivalent to system catalog.

It can refer to the table test, but it can not update it.

1. It can update the table test, but it can not reference it.
2. It can not reference or update the table test.
3. To restart the database, execute pg_ctl restart.
4. You can reference or update table test.

1. Since initdb needs to be run as an administrator user, run it as root user.
2. The directory of the database cluster specifies either a new directory or an existing empty directory.
3. If existing files exist in the database cluster directory, they are deleted.
4. Specify the directory of the database cluster using the command line argument of initdb or the environment variable PGDATA.
5. The character set specified by initdb is common to all databases in the cluster.

1. Tables can be added to the template database template0  like a normal (non template) database. 
2. Tables can be added to the template database template1 like a normal (non template) database. 

3. When you create a new database with CREATE DATABASE, unless specified in the option, template0 is used as a template database. 

4. To create a new template database called template2, add the TEMPLATE option when executing the CREATE DATABASE command.

5.  By default, no users can connect to the template database template0.

1. used for high availability, it is a mechanism to duplicate databases across multiple servers.
2. Immediately after installation, three databases, template0, template1, and postgres, are provided.

3. Only one database cluster can be created on one server.

4. Different versions of PostgreSQL server can be used for each database in the database cluster.