On 7/18/15 12:35 PM, Eli Collins wrote:
Hi All -
I'm currently trying to use sql.union() to construct a union of
sql.select() instances. My problem is that one of the columns in one
of the selects is an expression that takes a bind parameter, which is
causing an error.
I initially tried to code things as follows ...
|
fromsqlalchemy.sql import*
s1 =select([text("(:value || c3) as c1").bindparams(value='foo'),
column("c2")],from_obj=table("t1"))
s2 =select([column("c1"),column("c2")],from_obj=table("t2"))
u1 =union(s1,s2)
|
... however, union() throws/'Argument Error: All selectables passed to
CompoundSelect must have identical numbers of columns'./
Tracking this down, the problem seems to be that the first column of
s1 is a text() object, which doesn't get counted as a column when
union() tries to compare the column counts of the two select() clauses.
I've tried using literal_column(), but it doesn't support passing in a
text() element as it's value, nor does it have a bindparams() method.
use (bindparam("value", String) + column("c2")).label("c1")
I've run out of ideas for how to provide something "column-like" for
union(), while at the same time safely use bindparams() to pass in a
value.
I'm not sure if this is a bug, or if there's another construction I
should be using.
- Eli Collins
(P.S. I'm using SQLAlchemy 1.0.6; Python 2.7)
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