We will now get the numbers of records of each table by quivering on pg_stat_user_tables and showing them in decreasing order. The users are also able to enlist it by using information-schema and table objects. ![]() We can clearly see that there are 22 tables and view types of objects that are residing in the dvdrental database. Let me show you the number of tables and their tuples counts in the user database dvdrental beforehand, upgrading the Postgres server. Here, we can see that dvdrental is a user database, while Postgres is a system database. After that, I have used the \l command to get the list of all databases existing on the PostgreSQL. Here, the default port number 5432 is under use by my currently running PostgreSQL server, and the version of PostgreSQL 9.6.19. Below I will dictate the possible challenges, errors and its solution on my local server Using the VERSION() and inet_server_port() functions, users will get the information of PostgreSQL version and the port number on which PostgreSQL is running. Here, I used the directory, C:\Users\JERRY\Downloads\PostgreSQLDir\Backup, for storing the backup database and named it as 'dvrental' with a tar extension. Pg_dump -U Postgres -W -F t dvdrental > "V:\ PostgreSQL Backup\dvdrental.tar" Then run the pg_dump command, as shown here: CD C:\Program Files\PostgreSQL\9.0\bin To do this, open a command prompt and traverse through the appropriate directory. However, we can take a backup together of all databases using the pg_dumpall command. Users may take an individual database backup by using the help of the below command. ![]() It could be modified by the user to change the Config file with the 9.X version, so we have to compare config files of 9.X with 12.X and synch the required updates in the newer version's config file(12.x). The default directory where PostgreSQL keeps configuration file is: C:\Program Files\PostgreSQL \X.X\data). Two config files ( nf and pg_hba.conf) must be have a backup taken as the newer installation will replace the new config file with default configuration parameters and values. Generally, backing up of data is not essential as current PostgreSQL 9.x will not get affected during or after the update using the pg_upgrade process. The PostgreSQL Config file and user database file must be backed up using pg_dump command before initiating the PostgreSQL upgrade process. We will cover many requirements in-depth in this text to eradicate the numerous dynamic errors and challenges. Upgrading the PostgreSQL server can be done by installing the newer version of Postgres alongside the current one and executing the pg_upgrade command with essential parameters. A manual backup and restore process is not required when we use the pg_upgrade as the command will automatically copy the data directory to the newer version. Third, suppose you have to calculate the net price of every product based on the discount of the product segment.This text will elaborate on upgrading the PostgreSQL database from the 9.x version to the 12.x version. ( 'nulla elit ac', 161.71, 3) Code language: SQL (Structured Query Language) ( sql ) For example, products with the grand luxury segment have 5% discount while luxury and mass products have 6% and 10% discounts respectively.įOREIGN KEY(segment_id) REFERENCES product_segment( id) The product_segment table has the discount column that stores the discount percentage based on a specific segment. We will use the following database tables for the demonstration:įirst, create a new table called product_segment that stores the product segments including grand luxury, luxury, and mass. Let’s take a look at an example to understand how the PostgreSQL UPDATE join works. If the value in the c2 column of table t1 equals the value in the c2 column of table t2, the UPDATE statement updates the value in the c1 column of the table t1 the new value ( new_value). The FROM clause must appear immediately after the SET clause.įor each row of table t1, the UPDATE statement examines every row of table t2. To join to another table in the UPDATE statement, you specify the joined table in the FROM clause and provide the join condition in the WHERE clause. ![]() Code language: SQL (Structured Query Language) ( sql )
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