sql_mode=ORACLE: IS NULL and empty strings

DROP TABLE t1;

CREATE TABLE t1 (id INT NOT NULL, s VARCHAR(10) NOT NULL);

INSERT INTO t1 VALUES (1, '');

INSERT INTO t1 VALUES (1, '')

                          *

ERROR at line 1:

ORA-01400: cannot insert NULL into ("SYSTEM"."T1"."S")

DROP TABLE t1;

CREATE TABLE t1 (id INT NOT NULL, s VARCHAR(10));

INSERT INTO t1 VALUES (0, NULL);

INSERT INTO t1 VALUES (1, '');

INSERT INTO t1 VALUES (2, 'test');

SELECT * FROM t1 WHERE s IS NULL;

	ID S

---------- ----------

	 0

	 1

SELECT '' AS c1, NULL AS c2 FROM DUAL;

C C

- -

DROP TABLE t1;

CREATE TABLE t1 (v VARCHAR(10), c CHAR(10));

INSERT INTO t1 VALUES ('','');

SELECT v,c FROM t1;

V	   C

---------- ----------

DROP TABLE t1;

CREATE TABLE t1 (v VARCHAR(10));

INSERT INTO t1 VALUES ('');

SELECT * FROM t1 WHERE v='';

no rows selected

DROP TABLE t1;

CREATE TABLE t1 (v VARCHAR(10));

INSERT INTO t1 VALUES ('');

SELECT * FROM t1 WHERE v IS NULL;

V

----------

DROP TABLE t1;

CREATE TABLE t1 (c CHAR(10));

INSERT INTO t1 VALUES ('');

SELECT * FROM t1 WHERE c='';

no rows selected

DROP TABLE t1;

CREATE TABLE t1 (c CHAR(10));

INSERT INTO t1 VALUES ('');

SELECT * FROM t1 WHERE c IS NULL;

C

----------

DROP TABLE t1;

CREATE TABLE t1 (v VARCHAR(10));

INSERT INTO t1 VALUES ('');

SELECT v||'A' FROM t1;

V||'A'

-----------

A