![]() ![]() JSON operators + PostgreSQL aggregate functions Now lets select everything: SELECT * FROM events Populating the DB INSERT INTO books(client, data) values ( Firstly, we will log in to my psql command prompt and connect to my educba database.Example Creating a DB and a Table DROP DATABASE IF EXISTS books_db ĬREATE DATABASE books_db WITH ENCODING='UTF8' TEMPLATE template0 Let us perform the above-mentioned solution on our terminal. SELECT * FROM remote_educba_data WHERE technologies LIKE 'psql%' Example For example, using the same use-case as of above example we will create a view named remote_educba_data and later whenever required will retrieve the data from that view instead of using dblink and all that lengthy syntaxįor later usage, we will use the following query – We will just fire a select query on the view that we have created on our database. In this way, we will not have to mention the datatype and name of the column every time we want to retrieve the values from the remote database. During the run-time, if the column values retrieved from dblink() do not match the column count from the select query’s alias an error will be thrown saying that column count does not match with the retrieved results.Īs it is a very clumsy thing to mention the names of columns as well as the datatypes every time the dblink call is given, the most convenient way to do this is to create the view for the same. Specifying data types along with column names is the norm introduced and used in PostgreSQL while using the alias. Specifying names of the column was already compulsory in SQL syntax while using the alias. For example –įROM dblink('dbname=demoDatabaseName user=anyPostgresUser password=password_that_is_set options=-csearch_path=',ĪS demo(id integer, technologies varchar)Īs shown above, it is necessary to specify the column names in the SQL query password as a parameter to the dblink() method and while retrieving the records from the select query on the return value from dblink(), it is necessary to mention the name of the columns and the data type of the columns so that the system will understand that the column will take that much space after retrieving. The dblink() functions return the set of the rows as records and you need to specify the names of the columns you need to retrieve from the remote database’s table and as the retrieving query will not have any idea about the type of columns that will be fetched, it is required to specify the name of the columns as well as the data type of the columns that will be retrieved from dblink() call’s return value. If not then it goes for considering it as connection information string and builds up the connection accordingly. Hence, whenever two text parameters are supplied to the dblink method then firstly it goes for analyzing whether the first text parameter is any database connection name that exists. There are two syntaxes that have two text parameters at the beginning of it and have the same signature. When specified true or not specified it results in an error on your database when the error has occurred on the remote database and if the value is set to false then it raises the notice on your side when an error has occurred on the remote database server. fail_on_error – This is a boolean parameter that has the default value set to true when skipped or omitted in the specification as it is an optional parameter.query_statement – It is the query statement that you wish to execute on the remote database server to retrieve the rows stored there and that satisfy your query specifications.hostaddr=192.16.10.11 port=5432 dbname=demoDatabaseName user=anyPostgresUser password=password_that_is_set options=-c.The structure of that information string is somewhat like the following example – connection_string – It is the string that contains information about the database connection to be made with the remote database server in the libpq-style. ![]() It can even be skipped in case if you want to create an unnamed connection. ![]()
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