On 29 September 2010 19:15, Peter Bex <Peter.Bex@xxxxxxxxx> wrote: > On Wed, Sep 29, 2010 at 07:08:22PM +0100, Thom Brown wrote: >> Could someone explain why the following doesn't work? >> >> test=# PREPARE meow(unknown) AS >> test-# SELECT $1 as meow; >> ERROR: could not determine data type of parameter $1 >> >> The problem is that using PDO in PHP, prepared statements aren't >> possible if values are used instead of columns in the select list. > > The type is always string for data that's sent; it's converted to > an appropriate type when the destination of the parameter is determined. > If you know the type, you can do > > PREPARE meow(text) AS > SELECT $1 as meow; > > or > > PREPARE meow(unknown) AS > SELECT $1::text as meow; > > You can also send a parameter as a specific type using the C interface, > but that requires support from the language/library you're using. > >> This appears to be allowed for MySQL and SQL Server. > > I don't know how they handle that. Perhaps they try to read your mind. > Perhaps PHP adds some kind of type conversion for types it knows for > those two interfaces. Okay, I understand what's happening. But does the planner need to understand the type of literals in the select list if it's not used anywhere else? -- Thom Brown Twitter: @darkixion IRC (freenode): dark_ixion Registered Linux user: #516935 -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
