This is how we can check table existence in MSSQL:
IF OBJECT_ID(N'public."TABLE_NAME"', N'U') IS NOT NULL
select 1 as 'column'
else
select 0 as 'column';
which stores outcome in variable 'column'
How can I do same thing in PostgreSQL ? I want to return 1 or 0 for respective outcome.
Use a SELECT with an EXISTS operator checking e.g. information_schema.tables:
select exists (select *
from information_schema.tables
where table_name = 'table_name'
and table_schema = 'public') as table_exists;
If you can't (or won't) deal with proper boolean values, the simply cast the result to a number (but I have no idea why that should be better):
select exists (select *
from information_schema.tables
where table_name = 'table_name'
and table_schema = 'public')::int as "column";
Note that column is a reserved keyword and thus you need to quote it using double quotes.
Check for column in a table existence use view pg_tables
IF EXISTS ( SELECT attname
FROM pg_attribute
WHERE attrelid = (SELECT oid FROM pg_class WHERE relname = 'YOURTABLENAME')
AND attname = 'YOURCOLUMNNAME')
THEN
-- do something
END IF;
For my sql use INFORMATION_SCHEMA.COLUMNS
SELECT 1
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = 'tbl_name'
[AND table_schema = 'db_name']
[AND column_name LIKE 'wild']
Related
The problem is the following, how through a query in postgresl/pgadmin I can get all the tables with a specific column and that this column is not empty.
The solution I came to is the following.
SELECT relname, n_tup_ins
FROM pg_stat_all_tables
WHERE relname IN (
SELECT table_name
FROM information_schema.columns
WHERE column_name = 'company_id' AND table_schema = 'public' AND table_schema = 'company_id'.
AND table_schema = 'public'
)
ORDER BY n_tup_ins DESC
Where company_id is the column I was looking for.
I hope this helps someone.
I am trying to alter table based on another table dynamically.
Below is the piece of code i wrote in postgresql stored procedure.
But running out into some syntax errors.
Please help me here.
I just started working in postgresql and i am from sql server background. Like how we do in sql server print stmts do debug dynamic queries inside procedures; do we have any link to refer please share that as well. It would help me.
DROP TABLE IF EXISTS temp_table;
CREATE TEMP TABLE temp_table AS
with cte as
(
select column_name,data_type,character_maximum_length
from information_schema."columns" c
where table_name = 'customer_new' and table_schema = 'public'
and column_default is null
)
,cte1 as
(
select column_name,data_type,character_maximum_length
from information_schema."columns" c
where table_name = 'customer_old' and table_schema = 'public'
and column_default is null
)
select cte.column_name,
case when cte.character_maximum_length is not null then cte.data_type||'('||cte.character_maximum_length||')' else cte.data_type end as data_type
from cte
left join cte1 on cte.column_name = cte1.column_name
where cte1.column_name is null;
for v_column_name,v_data_type in SELECT column_name,data_type FROM temp_table
loop
execute format ('alter table %s add column %s %s ;', v_dump_table_name, v_column_name, v_data_type);
end loop;
DROP TABLE IF EXISTS temp_table;
Thanks in advance.
DROP TABLE IF EXISTS temp_table;
CREATE TEMP TABLE temp_table AS
with cte as
(
select column_name,data_type,character_maximum_length
from information_schema."columns" c
where table_name = 'customer_new' and table_schema = 'public'
and column_default is null
)
,cte1 as
(
select column_name,data_type,character_maximum_length
from information_schema."columns" c
where table_name = 'customer_old' and table_schema = 'public'
and column_default is null
)
select 'alter table '||v_dump_table_name||' add column '||cte2.column_name||' '||data_type
as col
from cte2;
for v_column in SELECT col FROM temp_table
loop
execute format ('%s ;', v_column);
end loop;
DROP TABLE IF EXISTS temp_table;
As in topic, I would like to know how can I check for a column being non-nullable?
For oracle I have:
SELECT Nullable
FROM user_tab_columns
WHERE table_name = 'TOP_VALIDATION_RULE'
AND column_name = 'ERROR_LEVEL'
but how to transform it for postgresql?
I tried something like this, but getting ERROR: column "is_nullable" does not exist:
SELECT is_nullable
FROM information_schema.tables
WHERE table_name = 'TOP_VALIDATION_RULE'
AND column_name = 'ERROR_LEVEL'
///EDIT
After modification:
SELECT is_nullable
FROM information_schema.columns
WHERE table_name = 'TOP_VALIDATION_RULE'
AND column_name = 'ERROR_LEVEL'
I get:
Use pg_attribute to check the column is NULLABLE OR NOT
SELECT attnotnull FROM pg_attribute WHERE attname = 'ERROR_LEVEL'
Note: The above query will return more than one row if the ERROR_LEVEL column appears in more than one table in the database.
I want to know tables' columns' sizes, to limit inputs' length in the form (I'm also checking it in the backend).
How can I know this?
Try this query, it returns all the column name, data type, maximum lengths for a given table 'table_name'.
SELECT column_name, data_type, character_maximum_length
FROM information_schema.columns
WHERE table_schema = 'public'
AND table_name = 'table_name';
You could modify it to return one column replacing 'column_name' with yours like so:
SELECT column_name, data_type, character_maximum_length
FROM information_schema.columns
WHERE table_schema = 'public'
AND table_name = 'table_name'
AND column_name = 'column_name';
I'm using PostgreSQL and I want to create a query that will display all column_names in a specific table.
Schema: codes
Table Name: watch_list
Here are the column_names in my table:
watch_list_id, watch_name, watch_description
I tried what I found in the web:
SELECT *
FROM information_schema.columns
WHERE table_schema = 'codes'
AND table_name = 'watch_list'
It output is not what I wanted. It should be:
watch_list_id, watch_name, watch_description
How to do this?
If you want all column names in a single row, you need to aggregate those names:
SELECT table_name, string_agg(column_name, ', ' order by ordinal_position) as columns
FROM information_schema.columns
WHERE table_schema = 'codes'
AND table_name = 'watch_list'
GROUP BY table_name;
If you remove the condition on the table name, you get this for all tables in that schema.
SELECT table_name FROM information_schema.tables WHERE table_schema='public'