Manlio Perillo wrote:
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>
> Hi.
>
> It seems there is a bug with SQL CASE support in SQLAlchemy (I'm testing
> using trunk).
>
> Here is the original SQL statements:
>
> CREATE TABLE test (
> x INTEGER PRIMARY KEY
> );
>
> SELECT
> CASE WHEN 'true'
> THEN (SELECT EXISTS (SELECT x FROM test))
> END;
>
>
> And here is the Python code:
>
> from sqlalchemy import schema, types, sql, create_engine
>
> metadata = schema.MetaData()
> test = schema.Table(
> 'test', metadata,
> schema.Column('x', types.Integer, primary_key=True)
> )
>
> engine = create_engine('sqlite://')
>
> subquery = sql.exists(test.select().as_scalar())
> clause = sql.case([(True, subquery.select().as_scalar)])
> query = clause.select()
>
> engine.execute(query)
its more SQLA not warning you about an argument it doesn't like and then
it leading into problems. it should raise an error earlier. basically
exists() is like a select() and accepts the list of column expressions as
a list. if you were to pass your select inside of a [], you'd get a
valid SQL expression, though with two levels of "select".
sql.exists([test]) or exists().select_from(test) would be more effective.
ill try to catch that issue now.
>
>
> I get an error:
>
> Traceback (most recent call last):
> File "case.py", line 13, in <module>
> subquery = sql.exists(test.select().as_scalar())
> File
> "/usr/local/lib/python2.5/site-packages/sqlalchemy/sql/expression.py",
> line 520, in exists
> return _Exists(*args, **kwargs)
> File
> "/usr/local/lib/python2.5/site-packages/sqlalchemy/sql/expression.py",
> line 2688, in __init__
> s = select(*args, **kwargs).as_scalar().self_group()
> File
> "/usr/local/lib/python2.5/site-packages/sqlalchemy/sql/expression.py",
> line 238, in select
> return Select(columns, whereclause=whereclause, from_obj=from_obj,
> **kwargs)
> File
> "/usr/local/lib/python2.5/site-packages/sqlalchemy/sql/expression.py",
> line 3492, in __init__
> if columns:
> File
> "/usr/local/lib/python2.5/site-packages/sqlalchemy/sql/expression.py",
> line 1289, in __nonzero__
> raise TypeError("Boolean value of this clause is not defined")
> TypeError: Boolean value of this clause is not defined
>
>
> I'm not sure if my code is correct.
> If it is not correct, what it the correct method to define that query?
>
>
>
> Thanks Manlio
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