Is there a better way to get a row of a table into hstore format than going
SELECT hstore(ARRAY['col1','col2','col3'], ARRAY[col1::text, col2::text, col3::text]) FROM tbl;
It works, but I figure there has to be a better way than typing out each column. hstore takes a record type for input, but I couldn't figure out how to feed the single-row producing query into the function and make it happy. Postgres version 9.0.4.
Yes - you can cast row to hstore type with hstore() function.
SELECT hstore(tbl.*) FROM tbl;
Works for me:
filip#filip=# select hstore(foo.*) from foo;
hstore
------------------------
"bar"=>"1", "baz"=>"2"
(1 row)
See http://www.postgresql.org/docs/9.0/static/hstore.html#HSTORE-FUNC-TABLE
Related
I'm fairly new to PostgreSQL specially to the whole set of functions it has to manage JSONs. I have this json example where I can grab always one element but, I want to map it to a new array:
select '{"a": {"b":{"c": [{"id":"foo"},{"id":"fuu"}]}}}'::json#>'{a,b,c}';
column
-----------------------------
[{"id":"foo"},{"id":"fuu"}]
(1 row)
What I really want is:
[foo, fuu]
If you are using Postgres 12 or newer you can use a JSON path query:
select jsonb_path_query_array(the_column, '$.a.b.c[*].id')
from the_table
This assumes that the column is a jsonb column (which it should be). If it's not you need to cast it: the_column::jsonb
I have a table. I wrote a function in plpgsql that inserts a row into this table:
INSERT INTO simpleTalbe (name,money) values('momo',1000) ;
This table has serial field called id. I want in the function after I insert the row to know the id that the new row received.
I thought to use:
select nextval('serial');
before the insert, is there a better solution?
Use the RETURNING clause. You need to save the result somewhere inside PL/pgSQL - with an appended INTO ..
INSERT INTO simpleTalbe (name,money) values('momo',1000)
RETURNING id
INTO _my_id_variable;
_my_id_variable must have been declared with a matching data type.
Related:
PostgreSQL next value of the sequences?
Depending on what you plan to do with it, there is often a better solution with pure SQL. Examples:
Combining INSERT statements in a data-modifying CTE with a CASE expression
PostgreSQL multi INSERT...RETURNING with multiple columns
select nextval('serial'); would not do what you want; nextval() actually increments the sequence, and then the INSERT would increment it again. (Also, 'serial' is not the name of the sequence your serial column uses.)
#Erwin's answer (INSERT ... RETURNING) is the best answer, as the syntax was introduced specifically for this situation, but you could also do a
SELECT currval('simpletalbe_id_seq') INTO ...
any time after your INSERT to retrieve the current value of the sequence. (Note the sequence name format tablename_columnname_seq for the automatically-defined sequence backing the serial column.)
I have a table named "temp_table" and a column named "temp_column" of type varchar. The problem is "temp_column" must be of type integer. If I will just automatically update the table into type integer, it will generate an error since some data has non-numeric data in it.
I want a query that will show all rows if "temp_column" has non-numeric values in it (or the other way around) and update or SET the value accordingly. I'm having a hard time since ISNUMERIC is not available in postgresql.
how to do this?
This will show all rows where you have non-integer values in that column. It uses a regular expression to find all values that have anything else than just numbers in it:
select *
from temp_table
where temp_column ~ '[^0-9]';
this can also be used in an update statement:
update temp_table
set temp_column = null
where temp_column ~ '[^0-9]';
This will also filter out "numeric" values like 3.14 as those aren't integers.
I wonder if someone could have an idea what is going wrong with this simple query on a hstore column in PostgreSQL 9.2
The queries are runned in pgAdmin
select attributeValue->"CODE_MUN" from shapefile_feature
returns: « attributevalue » column does not exists
when doing:
select * from shapefile_feature;
all the columns are returned including attributeValue, the hstore column
what is the problem?
PostgreSQL distinguish between "identifiers" and 'literal'. Identifiers are schema, table, column's, .. names, literals are others. A attribute in hstore are not SQL identifiers. So you have to pass their names as literals. Operator "->" is only shortcut for function "fetchval(hstore, text)" with possibility be indexed.
select attributeValue->'CODE_MUN' from shapefile_feature
is internally transformed to (don't do this transformation by self!)
select fetchval(attributeValue, 'CODE_MUN') from shapefile_feature
on buggy example in transformed form, you can better understand to error message:
select fetchval(attributeValue, "CODE_MUN") from shapefile_feature
PostgreSQL tries to find column "CODE_MUN" in shapefile_feature, bacause used double quotes means identifiers (in case sensitive notation).
I'm trying to create an index on the cast of a varchar column to date. I'm doing something like this:
CREATE INDEX date_index ON table_name (CAST(varchar_column AS DATE));
I'm getting the error: functions in index expression must be marked IMMUTABLE But I don't get why, the cast to date doesn't depends on the timezone or something like that (which makes a cast to timestamp with time zone give this error).
Any help?
Your first error was to store a date as a varchar column. You should not do that.
The proper fix for your problem is to convert the column to a real date column.
Now I'm pretty sure the answer to that statement is "I didn't design the database and I cannot change it", so here is a workaround:
CAST and to_char() are not immutable because they can return different values for the same input value depending on the current session's settings.
If you know you have a consistent format of all values in the table (which - if you had - would mean you can convert the column to a real date column) then you can create your own function that converts a varchar to a date and is marked as immutable.
create or replace function fix_bad_datatype(the_date varchar)
returns date
language sql
immutable
as
$body$
select to_date(the_date, 'yyyy-mm-dd');
$body$
ROWS 1
/
With that definition you can create an index on the expression:
CREATE INDEX date_index ON table_name (fix_bad_datatype(varchar_column));
But you have to use exactly that function call in your query so that Postgres uses it:
select *
from foo
where fix_bad_datatype(varchar_column) < current_date;
Note that this approach will fail badly if you have just one "illegal" value in your varchar column. The only sensible solution is to store dates as dates,
Please provide the database version, table ddl, and some example data.
Would making your own immutable function do what you want, like this? Also look into creating a new cast in the docs and see if that does anything for you.
create table emp2 (emp2_id integer, hire_date VARCHAR(100));
insert into emp2(hire_date)
select now();
select cast(hire_date as DATE)
from emp2
CREATE FUNCTION my_date_cast(VARCHAR) RETURNS DATE
AS 'select cast($1 as DATE)'
LANGUAGE SQL
IMMUTABLE
RETURNS NULL ON NULL INPUT;
CREATE INDEX idx_emp2_hire_date ON emp2 (my_date_cast(hire_date));