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SQuirreL SQL

SQuirreL SQL is an open-source graphical Java program that will allow you (among other things) to view the structure of a JDBC compliant database, browse the data in tables, and issue SQL commands. Its functionality can be extended by means of plug-ins; most of these allow SQuirreL to handle specific features of various database systems, but others make it possible to import data from Excel and CSV files, to compare the contents of tables, and to produce 'graphs' (E-R diagrams) of selected tables.

You can download SQuirreL from SourceForge, at squirrel-sql.sourceforge.net. It is made available under the GNU lesser general Public License, so that any SQL generated by the tool (to recreate or query tables, for example) should be freely usable as long as you own the copyright in the databases being queried. SQuirreL does not come with drivers for Polyhedra, so when you first run the tool you have to tell it where to find them. You do this by selecting the Drivers tab on the left hand side, and click on the + icon. This brings up a dialogue box:


Next, choose the Extra Class Path tab, click the Add button, and navigate to the directory containing the Polyhedra JDBC driver (which is called polyclasses.zip in Polyhedra 8.8 and earlier releases):


Select the ZIP file, and click the Open button: the pop-up will be closed, and the Polyhedra driver will appear in the Extra Class Path tab. Ensure is is selected, and click the List Drivers button, and SQuirreL will set the Class Name field for you:


Click OK to close the form; the driver is ready for use.


The next stage is to set up an 'alias', that allows you to open a particular database via the Polyhedra JDBC driver. Click on the Aliases tab on the left-hand side, and then click the + button to get a dialogue box that allows you to configure the alias. The diagram below shows an alias called 8001 that uses our newly-added driver to access a local database via the port 8001, with a dummy name and password:


There is no reason (other than to make it easier to remember things) to make the name of the alias match the port number that the database is (or will be) using.

When you click on the OK button, the dialogue box will close and the new alias will appear in the list. Double-click on it to open a connection, and you will first get a dialogue box asking for a user name and password, with default values as defined when the alias was created:



Once the connection is open, you will see some metadata for the database.


... and if you open up the list of tables and click one of them, you can inspect the contents:


Other interesting things you can do include producing entity-relationship diagrams, which SQuirreL calls 'graphs'. To do this, select a list of tables (by CTRL-clicking on their names), then right-clicking on one of them and selecting the 'Add to graph' option.