MySQL Cookbook

Database-Independent Methods of Obtaining Table Information

Problem

You want a way to get table information that doesn’t use MySQL-specific queries like SHOW COLUMNS.

Solution

This isn’t possible for all APIs. One exception is JDBC, which provides a standard interface to table metadata.

Discussion

The preceding methods for obtaining table information used specific SHOW or SELECT queries and showed how to process them using each API. These techniques are MySQL-specific. JDBC provides a way to access this information through a standard interface that makes no reference to particular queries, so you can use it portably with database engines other than MySQL. With this interface, you use your connection object to obtain a database metadata object, then invoke the getColumns( ) method of that object to retrieve column information. getColumns( ) returns a result set containing one row per column name, so you must run a fetch loop to retrieve information about successive columns. Elements of result set rows that are relevant for MySQL are:

Index	Meaning
3	Table name
4	Column name
6	Column type name
7	Column size (for numeric columns, this is the precision)
8	Number of decimal places, for numeric columns
18	Whether or not column values can be NULL

Here’s an example that shows how to use getColumns( ) to print a list of column names and types:

DatabaseMetaData md = conn.getMetaData ( ); ResultSet rs = md.getColumns (dbName, "", tblName, "%"); int i = 0; while (rs.next ( )) { i++; ...