Question

In a database that contains many tables, I need to write a SQL script to insert data if it is not exist.

Table currency

| id     | Code    | lastupdate | rate      |
+--------+---------+------------+-----------+
| 1      | USD     | 05-11-2012 | 2         |
| 2      | EUR     | 05-11-2012 | 3         |

Table client

| id     | name    | createdate | currencyId|
+--------+---------+------------+-----------+
| 4      | tony    | 11-24-2010 | 1         |
| 5      | john    | 09-14-2010 | 2         |

Table: account

| id     | number  | createdate | clientId  |
+--------+---------+------------+-----------+
| 7      | 1234    | 12-24-2010 | 4         |
| 8      | 5648    | 12-14-2010 | 5         |

I need to insert to:

1. currency (id=3, Code=JPY, lastupdate=today, rate=4)
2. client (id=6, name=Joe, createdate=today, currencyId=Currency with Code 'USD')
3. account (id=9, number=0910, createdate=today, clientId=Client with name 'Joe')

Problem:

1. script must check if row exists or not before inserting new data
2. script must allow us to add a foreign key to the new row where this foreign related to a row already found in database (as currencyId in client table)
3. script must allow us to add the current datetime to the column in the insert statement (such as createdate in client table)
4. script must allow us to add a foreign key to the new row where this foreign related to a row inserted in the same script (such as clientId in account table)

Note: I tried the following SQL statement but it solved only the first problem

INSERT INTO Client (id, name, createdate, currencyId)
SELECT 6, 'Joe', '05-11-2012', 1
WHERE not exists (SELECT * FROM Client where id=6);

this query runs without any error but as you can see I wrote createdate and currencyid manually, I need to take currency id from a select statement with where clause (I tried to substitute 1 by select statement but query failed).

This is an example about what I need, in my database, I need this script to insert more than 30 rows in more than 10 tables.

any help

Answer 1

You wrote

I tried to substitute 1 by select statement but query failed

But I wonder why did it fail? What did you try? This should work:

INSERT INTO Client (id, name, createdate, currencyId)
SELECT 
    6, 
    'Joe', 
    current_date, 
    (select c.id from currency as c where c.code = 'USD') as currencyId
WHERE not exists (SELECT * FROM Client where id=6);