I want to use JPA to create tables automatically by persistence.xml setting, but i found each sql must write in a single line and there must not have a semicolon just like below:
The first situation dose not work(because the code is not in a single line manner)
create table student(
id Integer,
name varchar2(50)
)
The Second situation dose not work neither(because a semicolon added at the end of the sql sentence):
create table school(id Integer, name varchar2(50));
create table student(id Integer, name varchar2(50),school_id Integer);
The SQLs listed below are correct(which have not semicolons in each line end, and every line is a standalone sql),but create a table SQL in a single line should not be friendly to read and maintain. Is anybody know a better way to resolve this issue?
create table school(id Integer, name varchar2(50))
create table student(id Integer, name varchar2(50),school_id Integer)
Related
I am trying to create a Postgres SQL-function which runs some routine for my database.
The SQL-function calls a plpgsql-function which creates several temporary tables, but doesn't return anything (RETURNS void).
One of the tables created by the plpgsql-function is supposed to be used in my sql-function.
CREATE OR REPLACE FUNCTION public.my_sql_function()
RETURNS text AS
$BODY$
select public.my_plpsql_function(); -- this returns void, but has created a temp table "tmp_tbl"
DROP TABLE IF EXISTS mytable CASCADE;
CREATE TABLE mytable (
skov_id int8 PRIMARY KEY,
skov_stor int4,
skov_areal_ha numeric,
virkningfra timestamp(0) without time zone,
plannoejagtighed float8,
vertikalnoejagtighed float8,
geom geometry(MultiPolygon,25832),
orig_geom geometry(Polygon, 25832)
);
INSERT INTO mytable
select * from tmp_tbl ....
$BODY$ LANGUAGE sql;
When I try to run the lines, I get the following error:
ERROR: relation "tmp_tbl" does not exist
pgAdmin underlines the line select * from tmp_tbl ... as the part with an error.
So the SQL-function doesn't notice that the plpsql-function has created a temporary table.
Is there a workaround?
Creating and accessing a table in the same SQL function is generally impossible. Makes no difference whether you create the table in the SQL function directly or in a nested function call. All objects must be visible to begin with.
There is a big, fat note at the top of the chapter Query Language (SQL) Functions in the manual pointing that out:
Note
The entire body of a SQL function is parsed before any of it is
executed. While a SQL function can contain commands that alter the
system catalogs (e.g., CREATE TABLE), the effects of such commands
will not be visible during parse analysis of later commands in the
function. Thus, for example, CREATE TABLE foo (...); INSERT INTO foo VALUES(...); will not work as desired if packaged up into a single
SQL function, since foo won't exist yet when the INSERT command is
parsed. It's recommended to use PL/pgSQL instead of a SQL function in
this type of situation.
Related:
Why can PL/pgSQL functions have side effect, while SQL functions can't?
Difference between language sql and language plpgsql in PostgreSQL functions
I think so it is not possible - and minimally it should not by possible in future versions. SQL functions are similar to views, and then references to database object should be valid in function's creating time.
There is not any workaround - if you need temp table, use PLpgSQL, or try to write your code without temp table (it can be much better).
So the thing is I am developing a contrib module and want to capture table name inside that contrib module.
question:
Is there any way to capture a table name during create table or insert table?
I have seen some of the triggers but not able to make it (I don't think there is any create table trigger). In case it is possible tell me a way to achieve it.
I though of extracting meta-data using pg_class but not helping it seems because I have to give explicitly a rel-name (table name) in where clause
do you think any other way to achieve it? Please elaborate if any and please let me know.
Here is some example which will make you understand a bit about the things I want to achieve.
creating a table:
create table new_table(name varchar , new integer);
insert into new_table values('abcdefghijkl' , 5004);
create table new_table1(name1 varchar , new1 integer) ;
insert into new_table1 values('mnopqrst' , 5005);
creating extension:
create extension table_name-extract;
select extract_tablename();
So my extension should extract a table name, means I should know table name with the built-in datatype I have declared.
Here what I expect as a output:
select extract_tablename();
table-name datatype-name
new_table name new
new_table1 name1 new1
You don't really need an extension to track the execution of DDL statements.
For that you can use an event trigger
The manual also has an example on how to write an event trigger using PL/pgSQL
CREATE OR REPLACE FUNCTION snitch()
RETURNS event_trigger
AS $$
BEGIN
RAISE NOTICE 'snitch: % %', tg_event, tg_tag;
END;
$$ LANGUAGE plpgsql;
CREATE EVENT TRIGGER snitch ON ddl_command_start
EXECUTE PROCEDURE snitch();
Inside the trigger function you would need to store the table name in some configuration table so that the information is not lost.
Of course you can package your trigger and "log table" (as a configuration table) into an extension if you want.
Another option is to enable DDL logging using
log_statement=ddl
in postgresql.conf - then you have all DDL statements in the Postgres logfile.
Whenever a execute a query such as :
CREATE TABLE myTable (myColumn INTEGER);
PostgreSQL automatically converts the Table and Column names to lowercase like this:
CREATE TABLE mytable (mycolumn INTEGER);
Is there any way to change the source code of PostgreSQL to avoid this automatic change?
I know the Double Quote method... But...
The Application I'm using is very large. So it is very difficult to change every occurrence of the query. Instead, I would like to change the source code of PostgreSQL which is found on GitHub.
You can use double quotes:
CREATE TABLE "myTable" ("myColumn" INTEGER);
We're in process of converting over from SQL Server to Postgres. I have a scenario that I am trying to accommodate. It involves inserting records from one table into another, WITHOUT listing out all of the columns. I realize this is not recommended practice, but let's set that aside for now.
drop table if exists pk_test_table;
create table public.pk_test_table
(
recordid SERIAL PRIMARY KEY NOT NULL,
name text
);
--example 1: works and will insert a record with an id of 1
insert into pk_test_table values(default,'puppies');
--example 2: fails
insert into pk_test_table
select first_name from person_test;
Error I receive in the second example:
column "recordid" is of type integer but expression is of type
character varying Hint: You will need to rewrite or cast the
expression.
The default keyword will tell the database to grab the next value.
Is there any way to utilize this keyword in the second example? Or some way to tell the database to ignore auto-incremented columns and just them be populated like normal?
I would prefer to not use a subquery to grab the next "id".
This functionality works in SQL Server and hence the question.
Thanks in advance for your help!
If you can't list column names, you should instead use the DEFAULT keyword, as you've done in the simple insert example. This won't work with a in insert into ... select ....
For that, you need to invoke nextval. A subquery is not required, just:
insert into pk_test_table
select nextval('pk_test_table_id_seq'), first_name from person_test;
You do need to know the sequence name. You could get that from information_schema based on the table name and inferring its primary key, using a function that takes just the table name as an argument. It'd be ugly, but it'd work. I don't think there's any way around needing to know the table name.
You're inserting value into the first column, but you need to add a value in the second position.
Therefore you can use INSERT INTO table(field) VALUES(value) syntax.
Since you need to fetch values from another table, you have to remove VALUES and put the subquery there.
insert into pk_test_table(name)
select first_name from person_test;
I hope it helps
I do it this way via a separate function- though I think I'm getting around the issue via the table level having the DEFAULT settings on a per field basis.
create table public.pk_test_table
(
recordid integer NOT NULL DEFAULT nextval('pk_test_table_id_seq'),
name text,
field3 integer NOT NULL DEFAULT 64,
null_field_if_not_set integer,
CONSTRAINT pk_test_table_pkey PRIMARY KEY ("recordid")
);
With function:
CREATE OR REPLACE FUNCTION func_pk_test_table() RETURNS void AS
$BODY$
INSERT INTO pk_test_table (name)
SELECT first_name FROM person_test;
$BODY$
LANGUAGE sql VOLATILE;
Then just execute the function via a SELECT FROM func_pk_test_table();
Notice it hasn't had to specify all the fields- as long as constraints allow it.
I am running following simple select query in PostgreSQL:
SELECT * FROM "INFORMATION_SCHEMA.KEY_COLUMN_USAGE"
It gives me following error report:
ERROR: relation "INFORMATION_SCHEMA.KEY_COLUMN_USAGE" does not exist
LINE 1: SELECT * FROM "INFORMATION_SCHEMA.KEY_COLUMN_USAGE"
^
********** Error **********
ERROR: relation "INFORMATION_SCHEMA.KEY_COLUMN_USAGE" does not exist
SQL state: 42P01
Character: 15
But when I am running the following query it runs successfully:
SELECT * FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
Again when I select from a table created by me the situation is reversed. Following one fails:
SELECT * FROM countryTable
while following one runs successfully.
SELECT * FROM "countryTable"
Why is it happening? What is the problem?
You probably created your table so:
CREATE TABLE "countryTable" (
id SERIAL NOT NULL,
country TEXT NOT NULL,
PRIMARY KEY(id)
);
Which create a tablespace wrapped in "", you shouldn't use double quote in general in postgres for table names or columns, try without double quotes:
CREATE TABLE countryTable (
id SERIAL NOT NULL,
country TEXT NOT NULL,
PRIMARY KEY(id)
);
An then you can use this query you already have SELECT * FROM countryTable
While my personal advice is to use legal, lower-case names exclusively and never use double-quote, it is no problem per se.
When you look at the table definition in psql (\d tbl), or at table names in the system catalog pg_class or column names in pg_attributes or any of the information schema views, you get identifiers in their correct spelling (and with all other oddities that may have been preserved by double-quoting them). You can use quote_ident() to quote such names automatically as needed - it only adds double quotes if necessary.
Postgres itself isn't foolish enough to use CaMeL case names. All objects in the information schema or in the system catalog are lower-cased (the names of the system tables and columns, not the names of user tables they carry as data).
Start at the basics, read the manual about identifiers.