Oracle 21c

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CREATE TABLE cust_trans (
  custno    CHAR(2),
  transdate DATE,
  transamt  NUMBER
);
INSERT INTO cust_trans (custno, transdate, transamt) VALUES (25, DATE '2007-01-01', 5000);
1 rows affected

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MM-RR';
SELECT transdate + '10' FROM cust_trans;

TRANSDATE+'10'

11-01-07

SELECT * FROM cust_trans WHERE transdate = '01-01-07';

CUSTNO
TRANSDATE
TRANSAMT

25
01-01-07
5000

SELECT transamt FROM cust_trans WHERE custno > '11';

TRANSAMT

5000

SELECT * FROM cust_trans WHERE transdate='01-JANUARY-07';

CUSTNO
TRANSDATE
TRANSAMT

25
01-01-07
5000

SELECT custno + 'A' FROM cust_trans WHERE transamt > 2000;
ORA-01722: invalid number