Re: Unable To Change Data Type

Carlos Mennens <carlos(dot)mennens(at)gmail(dot)com> wrote:

> For some reason I'm unable to change a column's TYPE from VARCHAR(20)
> to INTERGER or SMALLINT. I'm required to note the manufactures color
> code (value = 198) in the table data but keep getting this error and I
> don't understand why:
>
> The error I'm recieving is:
>
> ERROR: column "color" cannot be cast to type integer
>
> The table is defined as such:
>
> pearl=# \d reference
> Table "public.reference"
> Column | Type | Modifiers
> --------+-----------------------+--------------------------------------------------------
> id | integer | not null default
> nextval('reference_seq_id'::regclass)
> type | character varying(20) | not null
> size | smallint | not null
> color | character varying(20) | not null
> serial | integer |
> Indexes:
> "reference_pkey" PRIMARY KEY, btree (id)
> "reference_serial_key" UNIQUE, btree (serial)
>
> The data in the database appears as such:
>
> pearl=# SELECT id, color FROM reference ORDER BY id;
> id | color
> ----+-------
> 1 | 198
> 2 | 198
> 3 | 198
> 4 | 198
> 5 | 198
> 6 | 198
> (6 rows)
>
> Is this not possible to change the data type from VARCHAR to INTERGER
> or something numeric since only manufacturer color codes will be
> stored?

It's possible, but you have to use the correct syntax. See my example:

test=*# select * from foo;
t
---
1
2
3
4
(4 rows)

Time: 0,929 ms
test=*# alter table foo alter column t type int using (t::int);
ALTER TABLE
Time: 50,810 ms
test=*# \d foo;
Table "public.foo"
Column | Type | Modifiers
--------+---------+-----------
t | integer |

test=*# select * from foo;
t
---
1
2
3
4
(4 rows)

Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect. (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly." (unknown)
Kaufbach, Saxony, Germany, Europe. N 51.05082°, E 13.56889°