PostgreSQL Query

Use this activity to run a simple or a complex SQL Query on a database. The PostgreSQL Query activity returns information in the form of rows.

Settings

The Settings tab has the following field:

Field Description
Connection Name of the PostgreSQL database connection from where information is retrieved. You can select the connection from the Connection drop-down list.

Input Settings

The Input Settings tab has the following fields:

Field Description
Query An SQL statement used to query the database. The query can be a simple query or a complex query. A complex query has nested SQL statements. You can construct prepared SQL queries by using substitution variables (or parameters) of the form ?<fieldname> in the query statement. For example, select * from student where name = ?name;

Each substitution variable identifies an input parameter whose mapped value is substituted into the substitution variable at runtime. Input and Output tabs are populated based on the query.

End the query with semicolon (;) to fetch the metadata in the table at the bottom of the query.

The following examples represent simple and complex queries:

  • Simple query example:

    SELECT * FROM student;

    For the above query, the output fields are generated from the column information of the table student. 

    SELECT name, dept_name, tot_cred
    FROM student 
    WHERE dept_name = ?dept_name and tot_cred > ?tot_cred 
    ORDER BY dept_name;

    For the above query, output fields are generated for name, dept_name and tot_cred and input fields are generated for dept_name (varchar) and tot_cred (numeric). Also the mapped values for the fields, dept_name and tot_cred are substituted into the substitution variables ?dept_name and ?tot_cred at run time.

  • Nested query example: 

    SELECT *
    FROM (SELECT dept_name, SUM(tot_cred) AS total_credit
            FROM student
            GROUP BY dept_name) SUBS, department WHERE 
            SUBS.dept_name = department.dept_name AND total_credit > 8000;
Manually Configure Metadata Set the Manually Configure Metadata field to True to fetch table metadata manually. For more information, see Manually Configure Metadata.
Fields The grid is provided for informational purposes only.

Input

This tab contains the input schema. The fields that are selected on the Input Settings tab are available in the schema. You can either hard code their values or map them to a field from the output of a preceding activity in the flow using the Mapper.

Output

This tab displays the activity output schema in a tree structure format. The output of an activity is displayed for informational purposes only and cannot be modified or altered. The information in this schema varies depending on the fields that you selected on the Input Settings tab.

The properties that are displayed on the Output tab schema correspond to the output of this activity and can be used as input by subsequent activities in the flow.

Related concepts
Related reference