Receiving endless errors with the insert - statement - sql

Question

I am trying to insert some values into customer and then i get the ora-00904 error.
After i research about this problem, instead of using '' i used "". But now im receiving the ora-00984.
INSERT INTO customer (c_id, name, age)
VALUES (1, 'Carl', 45)
OUTPUT:
SQL-ERROR: ORA-00904: "name": invalid ID
00904. 00000 - "%s: invalid identifier"
then i tried this way.
INSERT INTO customer (c_id, name, age)
VALUES (1, "Carl", 45)
OUTPUT:
00984. 00000 - "column not allowed here"
My DDL - Code:
CREATE TABLE adress (
adress_id INTEGER NOT NULL,
state VARCHAR2(60) NOT NULL,
country VARCHAR2(60) NOT NULL
);
ALTER TABLE adress ADD CONSTRAINT adress_pk PRIMARY KEY ( adress_id );
CREATE TABLE contract (
con_id INTEGER NOT NULL,
length DATE
);
ALTER TABLE contract ADD CONSTRAINT contract_pk PRIMARY KEY ( con_id );
CREATE TABLE customer (
c_id INTEGER NOT NULL,
name VARCHAR2(60) NOT NULL,
age CHAR(2) NOT NULL,
adress_adress_id INTEGER
);
ALTER TABLE customer ADD CONSTRAINT customer_pk PRIMARY KEY ( c_id );
CREATE TABLE relation_1 (
customer_c_id INTEGER NOT NULL,
contract_con_id INTEGER NOT NULL
);
ALTER TABLE relation_1 ADD CONSTRAINT relation_1_pk PRIMARY KEY ( customer_c_id,
contract_con_id);
ALTER TABLE customer
ADD CONSTRAINT customer_adress_fk FOREIGN KEY ( adress_adress_id )
REFERENCES adress ( adress_id );
ALTER TABLE relation_1
ADD CONSTRAINT relation_1_contract_fk FOREIGN KEY ( contract_con_id )
REFERENCES contract ( con_id );
ALTER TABLE relation_1
ADD CONSTRAINT relation_1_customer_fk FOREIGN KEY ( customer_c_id )
REFERENCES customer ( c_id );

Answer 1

The syntax uses VALUES() for the list of values:
INSERT INTO customer (c_id, name, age)
VALUES (1, 'Carl', 45);
You can also use a SELECT:
INSERT INTO customer (c_id, name, age)
SELECT 1, 'Carl', 45
FROM dual;
Note that in both cases, the delimiter for the string is single quotes not double quotes.

Answer 2

In SQL we use single quotes for string literals. Double quotes are used (optionally) for identifiers such as table and column names. You have used double quotes around the value of carl and that's why Oracle hurls ORA-00984.
Why you got ORA-00904 for the first statement is a mystery. Probably there is something awry with your definition of customer but unless you post the table structure we cannot be sure.