Question: ```
SQL> desc invoices
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------

 INVOICE_ID                                NOT NULL NUMBER(6)
 COMPANY_ID                                         NUMBER(6)
 STUDENT_ID                                         NUMBER(6)
 BILLING_DATE                                       DATE

SQL>

```

I would like to insert some sample data into this table. The `company_id` and `student_id` are foreign keys. This is what I'am entering:

`INSERT INTO invoices
VALUES (SEQ_INVOICE.NEXTVAL,[what1],[what2],SYSDATE);`

I don't know what I am supposed to put in the what1 and what2

```
SQL> desc companies
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------

 COMPANY_ID                                NOT NULL NUMBER(6)
 COMPANY_NAME                                       VARCHAR2(30)
 ADDRESS                                            VARCHAR2(128)
 CONTACT_NO                                         VARCHAR2(11)
 NO_OF_EMP                                          NUMBER(10)

SQL>

SQL> desc students
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------

 STUDENT_ID                                NOT NULL NUMBER(6)
 ST_FNAME                                           VARCHAR2(16)
 ST_SNAME                                           VARCHAR2(16)
 ADDRESS                                            VARCHAR2(128)
 DOB                                                DATE

SQL>

```

Answer: 
you have to enter an existed `STUDENT_ID` from `students` table and an existed `COMPANY_ID` from `compaies` table to invoices.
Consider you have data like next

```
COMPANY_ID     COMPANY_NAME     ADDRESS     CONTACT_NO     NO_OF_EMP
-----------    ------------     --------    ----------     ---------
1              Blah LLC         blah st.    123456         100
2              My Company       My Street   987654321      50

```

and

```
STUDENT_ID     ST_FNAME     ST_SNAME     ADDRESS     DOB
-----------    ---------    ---------    --------    ------------
11             Jim          Carrey       ....        1900.25.04
22             Jack         Sparrow      Carrib st.  1700.30.08

```

then you can use `1` or `2` as `COMPANY_ID` (in your query [what1]) and `11` or `22` as `STUDENT_ID` (in your query [what2])
[what1] is ID of COMPANY\_ID
[what2] is ID of STUDENT\_ID
if table Student and Company are empty, you must Insert the record to both tables before Insert