Java JDBC with PostgreSQL: PreparedStatement Execute with Add Column Query returns false

Question

I am trying to add a column to a database table and

PreparedStatement  ps = con.prepareStatement(query);  
ps.execute();
ps.close();

query is something like (valid SQL)

ALTER TABLE mytable ADD COLUMN mycolumn datatypeinfo

Anyway, it executes fine and the column is created. But the execute statement returns false. I tried with executeUpdate and that returns 0 rows.

Note that this whole thing is within a transaction with con.setAutoCommit set to false. So I am not sure if that is the problem. The issue is that I have to create the column before I can go ahead with other update queries. So it has to run in a transaction.

Why not use the executeUpdate() method when you don't expect a ResultSet? docs.oracle.com/javase/6/docs/api/java/sql/… — kgrittn
– kgrittn, Commented May 2, 2012 at 18:42
I tried that, but it doesn't return anything. As it says, it returns 0 for SQL statements that return nothing, such as DDL statement. I guess I will just rely on whether an exception has been thrown. — Krishna
– Krishna, Commented May 2, 2012 at 18:47

user330315 · Accepted Answer · 2012-05-02 18:12:27Z

5

The return value of execute() does not indicate whether it was successful, but if the query that was run returned a result.

As the ALTER TABLE does not return a result, the execute() rightfully returns false

Quote from the Javadocs:

Returns: true if the first result is a ResultSet object; false if the first result is an update count or there is no result

answered May 2, 2012 at 18:12

user330315

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2 Comments

Krishna Over a year ago

Fair enough, but how do I check if the column has been added? Do I need to use DatabaseMetaData to go back to the table and check if it is in effect? (In essence, can I do it in one step instead of two?)

kgrittn Over a year ago

If it fails, it will throw an exception.

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