I'm very new to SQL developer and am now working with an existing Database. The tables do not have column comments and I've been tasked to add them. I created an excel spreadsheet of the column descriptions and imported as a table. I need to write a query for the table with the comments in a column (lets call it Table_1, comments) and insert those comments into the Column Comments for Table_2. If it helps there is a unique column_id number for each comment so comment for Table_1 should be inserted at comment row on Table_2 where Table_1.column_ID = Table_2.column_ID.
Thanks in adavance!
I have tried selecting the column from Table_1 and inserting as Comment on Column in Table_2 and got an error. Also tried reversing the order of these as well. I was able to insert each one individually using:
-Comment on Column table_name.column_name is 'this comment';
But it is tedious and I want to enter all of the comments at once using a query.
This is about adding a comment to table's column in data dictionary. To do that, you'll need dynamic SQL. Here's an example.
SQL> set serveroutput on
This is table that contains comments you'd want to apply:
SQL> select * from comments;
TABLE_NAME COLUMN_NAME COMMENTS
---------- ------------ ------------------------------
DEPT DEPTNO Department ID
DEPT DNAME Department name
EMP SAL Salary (USD)
For example, DEPT table currently doesn't have any comments:
SQL> select table_name, column_name, comments
2 from user_col_comments
3 where table_name = 'DEPT';
TABLE_NAME COLUMN_NAME COMMENTS
---------- ------------ ------------------------------
DEPT DEPTNO
DEPT DNAME
DEPT LOC
Procedure displays command which is then being executed:
SQL> declare
2 l_str varchar2(2000);
3 begin
4 for cur_r in (select table_name, column_name, comments
5 from comments
6 )
7 loop
8 l_str := 'comment on column ' || cur_r.table_name ||'.'||
9 cur_r.column_name || ' is ' || chr(39) || cur_r.comments || chr(39);
10 dbms_output.put_line(l_str);
11 execute immediate l_str;
12 end loop;
13 end;
14 /
comment on column DEPT.DEPTNO is 'Department ID'
comment on column DEPT.DNAME is 'Department name'
comment on column EMP.SAL is 'Salary (USD)'
PL/SQL procedure successfully completed.
Result:
SQL> select table_name, column_name, comments
2 from user_col_comments
3 where table_name = 'DEPT';
TABLE_NAME COLUMN_NAME COMMENTS
---------- ------------ ------------------------------
DEPT DEPTNO Department ID
DEPT DNAME Department name
DEPT LOC
SQL>
Related
I have a dataset that looks something like this:
I'd like to aggregate all co values on one row, so the final result looks something like:
Seems pretty easy, right? Just write a query using crosstab, as suggested in this answer. Problem is that requires that I CREATE EXTENSION tablefunc; and I don't have write access to my DB.
Can anyone recommend an alternative?
Conditional aggregation:
SELECT co,
MIN(CASE WHEN ontology_type = 'industry' THEN tags END) AS industry,
MIN(CASE WHEN ontology_type = 'customer_type' THEN tags END) AS customer_type,
-- ...
FROM tab_name
GROUP BY co
You can use DO to generate and PREPARE your own SQL with crosstab columns, then EXECUTE it.
-- replace tab_name to yours table name
DO $$
DECLARE
_query text;
_name text;
BEGIN
_name := 'prepared_query';
_query := '
SELECT co
'||(SELECT ', '||string_agg(DISTINCT
' string_agg(DISTINCT
CASE ontology_type WHEN '||quote_literal(ontology_type)||' THEN tags
ELSE NULL
END, '',''
) AS '||quote_ident(ontology_type),',')
FROM tab_name)||'
FROM tab_name
GROUP BY co
';
BEGIN
EXECUTE 'DEALLOCATE '||_name;
EXCEPTION
WHEN invalid_sql_statement_name THEN
END;
EXECUTE 'PREPARE '||_name||' AS '||_query;
END
$$;
EXECUTE prepared_query;
Since Ver. 9.4 there's json_object_agg(), which lets us do part of the necessary magic dynamically.
However to be totally dynamic, a temp type (a temp table) has to be FIRST built by running a SQL-EXEC inside an anonymous procedure.
DB FIDDLE (UK):
https://dbfiddle.uk/Sn7iO4zL
DISCLAIMER: Typically the ability to create TEMP TABLES are granted to end-users, but YMMV. Another concern is whether anon. procedures can be exec'd as in-line code by regular users.
-- /**
-- begin test data
-- begin test data
-- begin test data
-- */
DROP TABLE IF EXISTS tmpSales ;
CREATE TEMP TABLE tmpSales AS
SELECT
sale_id
,TRUNC(RANDOM()*12)+1 AS book_id
,TRUNC(RANDOM()*100)+1 AS customer_id
,(date '2010-01-01' + random() * (timestamp '2016-12-31' - timestamp '2010-01-01')) AS sale_date
FROM generate_series(1,10000) AS sale_id;
DROP TABLE IF EXISTS tmp_month_total ;
CREATE TEMP TABLE tmp_month_total AS
SELECT
date_part( 'year' , sale_date ) AS year
,date_part( 'month', sale_date ) AS mn
,to_char(sale_date, 'mon') AS month
,COUNT(*) AS total
FROM tmpSales
GROUP BY date_part('year', sale_date), to_char(sale_date, 'mon') ,date_part( 'month', sale_date )
;
DATA:
+----+--+-----+-----+
|year|mn|month|total|
+----+--+-----+-----+
|2010|1 |jan |127 |
|2010|2 |feb |117 |
|2010|3 |mar |121 |
|2010|4 |apr |131 |
|2010|5 |may |106 |
|2010|6 |jun |121 |
|2010|7 |jul |129 |
|2010|8 |aug |114 |
|2010|9 |sep |115 |
|2010|10|oct |110 |
|2010|11|nov |133 |
|2010|12|dec |108 |
+----+--+-----+-----+
-- /**
-- END test data
-- END test data
-- END test data
-- */
-- /**
-- dyn. build a temporary row-type based on existing data, not hard-coded
-- dyn. build a temporary row-type based on existing data, not hard-coded
-- dyn. build a temporary row-type based on existing data, not hard-coded
-- **/
DROP TABLE IF EXISTS tmpTblTyp CASCADE ;
DO LANGUAGE plpgsql $$ DECLARE v_sqlstring VARCHAR = ''; BEGIN
v_sqlstring := CONCAT( 'CREATE TEMP TABLE tmpTblTyp AS SELECT '
,(SELECT STRING_AGG( CONCAT('NULL::int AS ' , month )::TEXT , ' ,'
ORDER BY mn
)::TEXT
FROM
(SELECT DISTINCT month, mn FROM tmp_month_total )a )
,' LIMIT 0 '
) ; -- RAISE NOTICE '%', v_sqlstring ;
EXECUTE( v_sqlstring ) ; END $$;
DROP TABLE IF EXISTS tmpMoToJson ;
CREATE TEMP TABLE tmpMoToJson AS
SELECT
year AS year
,(json_build_array( months )) AS js_months_arr
,json_populate_recordset ( NULL::tmpTblTyp /** use temp table as a record type!! **/
, json_build_array( months )
) jprs /** builds row-type column that can be expanded with (jprs).*
**/
FROM ( SELECT year
-- accum data into JSON array
,json_object_agg(month,total) AS months
FROM tmp_month_total
GROUP BY year
ORDER BY year
) a
;
SELECT
year
,(ROW((jprs).*)::tmpTblTyp).* -- explode the composite type row
FROM tmpMoToJson ;
+----+---+---+---+---+---+---+---+---+---+---+---+---+
|year|jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec|
+----+---+---+---+---+---+---+---+---+---+---+---+---+
|2010|127|117|121|131|106|121|129|114|115|110|133|108|
|2011|117|112|117|115|139|116|119|152|117|112|115|103|
|2012|129|111|98 |140|109|131|114|110|112|115|100|121|
|2013|128|112|141|127|141|102|113|109|111|110|123|116|
|2014|129|114|117|118|111|123|106|111|127|121|124|145|
|2015|118|113|131|122|120|121|140|114|118|108|114|131|
|2016|117|110|139|100|110|116|112|109|131|117|122|132|
+----+---+---+---+---+---+---+---+---+---+---+---+---+
By using pivot also we can achieve your required out put
SELECT co
,industry
,customer_type
,product_type
,sales_model
,stage
FROM dataSet
PIVOT(max(tags) FOR ontologyType IN (
industry
,customer_type
,product_type
,sales_model
,stage
)) AS PVT
Assuming I have a parent table with child partitions that are created based on the value of a field.
If the value of that field changes, is there a way to have Postgres automatically move the row into the appropriate partition?
For example:
create table my_table(name text)
partition by list (left(name, 1));
create table my_table_a
partition of my_table
for values in ('a');
create table my_table_b
partition of my_table
for values in ('b');
In this case, if I change the value of name in a row from aaa to bbb, how can I get it to automatically move that row into my_table_b.
When I tried to do that, (i.e. update my_table set name = 'bbb' where name = 'aaa';), I get the following error:
ERROR: new row for relation "my_table_a" violates partition constraint
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=f0e44751d7175fa3394da2c8f85e3ceb3cdbfe63
it doesn't handle updates that cross partition boundaries.
thus you need to create one yourself... here's your set:
t=# insert into my_table select 'abc';
INSERT 0 1
t=# insert into my_table select 'bcd';
INSERT 0 1
t=# select tableoid::regclass,* from my_table;
tableoid | name
------------+------
my_table_a | abc
my_table_b | bcd
(2 rows)
here's rule and fn():
t=# create or replace function puf(_j json,_o text) returns void as $$
begin
raise info '%',': '||left(_j->>'name',1);
execute format('insert into %I select * from json_populate_record(null::my_table, %L)','my_table_'||left(_j->>'name',1), _j);
execute format('delete from %I where name = %L','my_table_'||left(_o,1), _o);
end;
$$language plpgsql;
CREATE FUNCTION
t=# create rule psr AS ON update to my_table do instead select puf(row_to_json(n),OLD.name) from (select NEW.*) n;
CREATE RULE
here's update:
t=# update my_table set name = 'bbb' where name = 'abc';
INFO: : b
puf
-----
(1 row)
UPDATE 0
checking result:
t=# select tableoid::regclass,* from my_table;
tableoid | name
------------+------
my_table_b | bcd
my_table_b | bbb
(2 rows)
once again:
t=# update my_table set name = 'a1' where name = 'bcd';
INFO: : a
puf
-----
(1 row)
UPDATE 0
t=# select tableoid::regclass,* from my_table;
tableoid | name
------------+------
my_table_a | a1
my_table_b | bbb
(2 rows)
Of course using json to pass NEW record looks ugly. And it is ugly indeed. But I did not have time to study the new PARTITION feature of 10, so don't know the elegant way to do this task. Hopefully I could give the generic idea of how you can possible solve the problem and you will produce a better neat code.
update
its probablygood idea to limit such rule to ON update to my_table where left(NEW.name,1) <> left(OLD.name,1) do instead, to release the heavy manipulations need
I am trying to write sub-queries so that I search all tables for a column named id and since there are multiple tables with id column, I want to add the condition, so that id = 3119093.
My attempt was:
Select *
from information_schema.tables
where id = '3119093' and id IN (
Select table_name
from information_schema.columns
where column_name = 'id' );
This didn't work so I tried:
Select *
from information_schema.tables
where table_name IN (
Select table_name
from information_schema.columns
where column_name = 'id' and 'id' IN (
Select * from table_name where 'id' = 3119093));
This isn't the right way either. Any help would be appreciated. Thanks!
A harder attempt is:
CREATE OR REPLACE FUNCTION search_columns(
needle text,
haystack_tables name[] default '{}',
haystack_schema name[] default '{public}'
)
RETURNS table(schemaname text, tablename text, columnname text, rowctid text)
AS $$
begin
FOR schemaname,tablename,columnname IN
SELECT c.table_schema,c.table_name,c.column_name
FROM information_schema.columns c
JOIN information_schema.tables t ON
(t.table_name=c.table_name AND t.table_schema=c.table_schema)
WHERE (c.table_name=ANY(haystack_tables) OR haystack_tables='{}')
AND c.table_schema=ANY(haystack_schema)
AND t.table_type='BASE TABLE'
--AND c.column_name = "id"
LOOP
EXECUTE format('SELECT ctid FROM %I.%I WHERE cast(%I as text) like %L',
schemaname,
tablename,
columnname,
needle
) INTO rowctid;
IF rowctid is not null THEN
RETURN NEXT;
END IF;
END LOOP;
END;
$$ language plpgsql;
select * from search_columns('%3119093%'::varchar,'{}'::name[]) ;
The only problem is this code displays the table name and column name. I have to then manually enter
Select * from table_name where id = 3119093
where I got the table name from the code above.
I want to automatically implement returning rows from a table but I don't know how to get the table name automatically.
I took the time to make it work for you.
For starters, some information on what is going on inside the code.
Explanation
function takes two input arguments: column name and column value
it requires a created type that it will be returning a set of
first loop identifies tables that have a column name specified as the input argument
then it forms a query which aggregates all rows that match the input condition inside every table taken from step 3 with comparison based on ILIKE - as per your example
function goes into the second loop only if there is at least one row in currently visited table that matches specified condition (then the array is not null)
second loop unnests the array of rows that match the condition and for every element it puts it in the function output with RETURN NEXT rec clause
Notes
Searching with LIKE is inefficient - I suggest adding another input argument "column type" and restrict it in the lookup by adding a join to pg_catalog.pg_type table.
The second loop is there so that if more than 1 row is found for a particular table, then every row gets returned.
If you are looking for something else, like you need key-value pairs, not just the values, then you need to extend the function. You could for example build json format from rows.
Now, to the code.
Test case
CREATE TABLE tbl1 (col1 int, id int); -- does contain values
CREATE TABLE tbl2 (col1 int, col2 int); -- doesn't contain column "id"
CREATE TABLE tbl3 (id int, col5 int); -- doesn't contain values
INSERT INTO tbl1 (col1, id)
VALUES (1, 5), (1, 33), (1, 25);
Table stores data:
postgres=# select * From tbl1;
col1 | id
------+----
1 | 5
1 | 33
1 | 25
(3 rows)
Creating type
CREATE TYPE sometype AS ( schemaname text, tablename text, colname text, entirerow text );
Function code
CREATE OR REPLACE FUNCTION search_tables_for_column (
v_column_name text
, v_column_value text
)
RETURNS SETOF sometype
LANGUAGE plpgsql
STABLE
AS
$$
DECLARE
rec sometype%rowtype;
v_row_array text[];
rec2 record;
arr_el text;
BEGIN
FOR rec IN
SELECT
nam.nspname AS schemaname
, cls.relname AS tablename
, att.attname AS colname
, null::text AS entirerow
FROM
pg_attribute att
JOIN pg_class cls ON att.attrelid = cls.oid
JOIN pg_namespace nam ON cls.relnamespace = nam.oid
WHERE
cls.relkind = 'r'
AND att.attname = v_column_name
LOOP
EXECUTE format('SELECT ARRAY_AGG(row(tablename.*)::text) FROM %I.%I AS tablename WHERE %I::text ILIKE %s',
rec.schemaname, rec.tablename, rec.colname, quote_literal(concat('%',v_column_value,'%'))) INTO v_row_array;
IF v_row_array is not null THEN
FOR rec2 IN
SELECT unnest(v_row_array) AS one_row
LOOP
rec.entirerow := rec2.one_row;
RETURN NEXT rec;
END LOOP;
END IF;
END LOOP;
END
$$;
Exemplary call & output
postgres=# select * from search_tables_for_column('id','5');
schemaname | tablename | colname | entirerow
------------+-----------+---------+-----------
public | tbl1 | id | (1,5)
public | tbl1 | id | (1,25)
(2 rows)
Database is called 'school'. 'school' has tables with 'classroom_names' i.e 'room1' as a table, 'room2' as another table, etc. and each 'classroom_names' has a 'student_name' column.
I want to select all 'classroom_names' where it has a 'student_name' called 'John'.
So far I can only select all 'classroom_names' from the database like his:
select * from syscat.tables
I'd suggest the following. (Which tries to fix some of the problems with your design)
Create the following View
CREATE OR REPLACE VIEW SCHOOL.STUDENT_LIST AS
SELECT 'Room1' as CLASSROOM, student_name FROM SCHOOL.Room1
UNION ALL
SELECT 'Room2' as CLASSROOM, student_name FROM SCHOOL.Room2
UNION ALL
SELECT 'Room3' as CLASSROOM, student_name FROM SCHOOL.Room3
UNION ALL
SELECT 'Room4' as CLASSROOM, student_name FROM SCHOOL.Room4
UNION ALL
-- etc
SELECT 'RoomN' as CLASSROOM, student_name FROM SCHOOL.RoomN
Now you can say
SELECT CLASSROOM FROM STUDENT_LIST WHERE student_name = 'John'
You can built a dynamic query from the DB2 catalog
db2 "select 'select ' || trim(tabname) || ' classroom, student_name from '
|| tabname || ' where student_name = ''John'';'
from syscat.tables
where tabname like 'room%'" | db2 +p -tv
The last part (db2 +p -tv) allows to execute the output. If it does not work (buffer size), just remove this, and copy paste the output.
In Postgres 8.4 or higher, what is the most efficient way to get a row of data populated by defaults without actually creating the row. Eg, as a transaction (pseudocode):
create table "mytable"
(
id serial PRIMARY KEY NOT NULL,
parent_id integer NOT NULL DEFAULT 1,
random_id integer NOT NULL DEFAULT random(),
)
begin transaction
fake_row = insert into mytable (id) values (0) returning *;
delete from mytable where id=0;
return fake_row;
end transaction
Basically I'd expect a query with a single row where parent_id is 1 and random_id is a random number (or other function return value) but I don't want this record to persist in the table or impact on the primary key sequence serial_id_seq.
My options seem to be using a transaction like above or creating views which are copies of the table with the fake row added but I don't know all the pros and cons of each or whether a better way exists.
I'm looking for an answer that assumes no prior knowledge of the datatypes or default values of any column except id or the number or ordering of the columns. Only the table name will be known and that a record with id 0 should not exist in the table.
In the past I created the fake record 0 as a permanent record but I've come to consider this record a type of pollution (since I typically have to filter it out of future queries).
You can copy the table definition and defaults to the temp table with:
CREATE TEMP TABLE table_name_rt (LIKE table_name INCLUDING DEFAULTS);
And use this temp table to generate dummy rows. Such table will be dropped at the end of the session (or transaction) and will only be visible to current session.
You can query the catalog and build a dynamic query
Say we have this table:
create table test10(
id serial primary key,
first_name varchar( 100 ),
last_name varchar( 100 ) default 'Tom',
age int not null default 38,
salary float default 100.22
);
When you run following query:
SELECT string_agg( txt, ' ' order by id )
FROM (
select 1 id, 'SELECT ' txt
union all
select 2, -9999 || ' as id '
union all
select 3, ', '
|| coalesce( column_default, 'null'||'::'||c.data_type )
|| ' as ' || c.column_name
from information_schema.columns c
where table_schema = 'public'
and table_name = 'test10'
and ordinal_position > 1
) xx
;
you will get this sting as a result:
"SELECT -9999 as id , null::character varying as first_name ,
'Tom'::character varying as last_name , 38 as age , 100.22 as salary"
then execute this query and you will get the "phantom row".
We can build a function that build and excecutes the query and return our row as a result:
CREATE OR REPLACE FUNCTION get_phantom_rec (p_i test10.id%type )
returns test10 as $$
DECLARE
v_sql text;
myrow test10%rowtype;
begin
SELECT string_agg( txt, ' ' order by id )
INTO v_sql
FROM (
select 1 id, 'SELECT ' txt
union all
select 2, p_i || ' as id '
union all
select 3, ', '
|| coalesce( column_default, 'null'||'::'||c.data_type )
|| ' as ' || c.column_name
from information_schema.columns c
where table_schema = 'public'
and table_name = 'test10'
and ordinal_position > 1
) xx
;
EXECUTE v_sql INTO myrow;
RETURN myrow;
END$$ LANGUAGE plpgsql ;
and then this simple query gives you what you want:
select * from get_phantom_rec ( -9999 );
id | first_name | last_name | age | salary
-------+------------+-----------+-----+--------
-9999 | | Tom | 38 | 100.22
I would just select the fake values as literals:
select 1 id, 1 parent_id, 1 user_id
The returned row will be (virtually) indistinguishable from a real row.
To get the values from the catalog:
select
0 as id, -- special case for serial type, just return 0
(select column_default::int -- Cast to int, because we know the column is int
from INFORMATION_SCHEMA.COLUMNS
where table_name = 'mytable'
and column_name = 'parent_id') as parent_id,
(select column_default::int -- Cast to int, because we know the column is int
from INFORMATION_SCHEMA.COLUMNS
where table_name = 'mytable'
and column_name = 'user_id') as user_id;
Note that you must know what the columns are and their type, but this is reasonable. If you change the table schema (except default value), you would need to tweak the query.
See the above as a SQLFiddle.