postgresql constraint (field a > field b)

Question

I'm doing a tastrade schema off the data our lecturers gave us. I'm using the SQL Pane to build the table and not the graphical userface (of PgAdminIII)

I have these 2:

12   MAX_ORDER_AMT Curr       8      4    max_order_amt > min_order_amt
13   MIN_ORDER_AMT.Curr       8      4    max_order_amt > min_order_amt
...
...

in order to create it I used [partial code]

"Max_Order_Amt" money,
"Min_Order_Amt" money,
...
...

In order to add the Max_Order_amt > min_order_amt constraint, what do I have to use?

I tried using "max_order_amt > min_order_amt" but it failed.

Thanks a lot for your help

Language Used: PostegreSQL

Graphical Userface PgAdminIII

EDIT: This is the FULL CREATE TABLE Code

CREATE TABLE oltp.customer
("Customer_ID" character (6) NOT NULL,
"Company_Name" character (40) NOT NULL,
"Contact_Name" character (30) NOT NULL,
"Address" character (60),
"City" character (15),
"Region" character(15),
"Postal_Code" character(10),
"Phone" character(24),
"Fax" character(24),
"Max_Order_Amt" money CHECK (Max_Order_Amt > Min_Order_Amt),
"Min_Order_Amt" money CHECK (Max_Order_Amt > Min_Order_Amt),
"Discount" numeric(2) CHECK (Discount >=0),
"Sales_Region" character(4),
CONSTRAINT customers_pkey PRIMARY KEY ("Customer_ID"))
WITH 
( OIDS = FALSE);
alter table oltp.customer
OWNER to postgres;

---

ERROR:  column "max_order_amt" does not exist

********** Error **********

ERROR: column "max_order_amt" does not exist
SQL state: 42703

---

This Below is the Tastrade Schema

CUSTOMER
(Customer Information)
Beware of updating or deleting instances from this table as other tables refer to this table’s PK
Number of data records:       92      
Fd   Field Name    Type   Width    Dec   Notes
 1   CUSTOMER_ID   Char       6          PK, system generated, not null
 2   COMPANY_NAME  Char      40          not null
 3   CONTACT_NAME  Char      30          not null
 4   CONTACT_TITLE Char      40          
 5   ADDRESS       Char      60          
 6   CITY          Char      15          
 7   REGION        Char      15          
 8   POSTAL_CODE   Char      10          
 9   COUNTRY       Char      15          
10   PHONE         Char      24          
11   FAX           Char      24          
12   MAX_ORDER_AMT Curr       8      4    max_order_amt > min_order_amt
13   MIN_ORDER_AMT.Curr       8      4    max_order_amt > min_order_amt
14   DISCOUNT      Nume       2           discount >= 0
15   SALES_REGION  Char       4          
** Total **                       302   

In the tastarade Schema Lines 12-14 are giving me the the 'does not exist' error. I have followed the 8.1 manual. It stops at Max_Order_Amt, but when I tried on the others, it gave me the same error

Thx again

Answer 1

Use a check constraint while creating your table like

"Max_Order_Amt" money CHECK (Max_Order_Amt > Min_Order_Amt)

See more about Check constraint here http://www.postgresql.org/docs/8.1/static/ddl-constraints.html

EDIT:

Remove those " double quotes around column name. Try it like below

CREATE TABLE customer
(Customer_ID character (6) NOT NULL,
Company_Name character (40) NOT NULL,
Contact_Name character (30) NOT NULL,
Address character (60),
City character (15),
Region character(15),
Postal_Code character(10),
Phone character(24),
Fax character(24),
Max_Order_Amt money CHECK (Max_Order_Amt > Min_Order_Amt),
Min_Order_Amt money,
Discount numeric(2) CHECK (Discount >=0),
Sales_Region character(4),
 CONSTRAINT customers_pkey PRIMARY KEY (Customer_ID));

See a demo fiddle here http://sqlfiddle.com/#!15/60767

EDIT1:

If you really want to keep " around your column name (for some reason) then make your check constraint looks like below

"Max_Order_Amt" money CHECK ("Max_Order_Amt" > "Min_Order_Amt"),
"Min_Order_Amt" money CHECK ("Max_Order_Amt" > "Min_Order_Amt"),
"Discount" numeric(2) CHECK ("Discount" >=0),