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#### 4.1.1.12 SQL Database Queries

With appropriate configuration, TOPCAT can be used to examine the results of queries on an SQL-compatible relational database.

Database queries can be specified as a string in the form:

       jdbc:driver-specific-url#sql-query

The exact form is dependent on the driver. Here is an example for MySQL:

       jdbc:mysql://localhost/astro1?user=mbt#SELECT ra, dec FROM swaa WHERE vmag<18

which would get a two-column table (the columns being "ra" and "dec"), constructed from certain rows from the table "swaa" in the database "astro1" on the local host, using the access privileges of user mbt.

Fortunately you don't have to construct this by hand, there is an SQL Query Dialogue to assist in putting it together.

Note that TOPCAT does not view a table in the database directly, but the result of an SQL query on that table. If you want to view the whole table you can use the query

       SELECT * FROM table-name

but be aware that such a query might be expensive on a large table.

Use of SQL queries requires some additional configuration of TOPCAT; see Section 10.3.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk