CREATE TABLE INT4_TBL(f1 int4);

INSERT INTO INT4_TBL(f1) VALUES ('   0  ');
INSERT INTO INT4_TBL(f1) VALUES ('123456     ');
INSERT INTO INT4_TBL(f1) VALUES ('    -123456');
INSERT INTO INT4_TBL(f1) VALUES ('2147483647');
INSERT INTO INT4_TBL(f1) VALUES ('-2147483647');

CREATE TABLE int4_tbl(f1 int4);

INSERT INTO int4_tbl
SELECT * FROM INT4_TBL;