MySQL 5.6

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CREATE TABLE BU_REF_NO 
   (           END_DATE VARCHAR(255)
   );


INSERT INTO BU_REF_NO (END_DATE) VALUES ('12 103 501');
INSERT INTO BU_REF_NO (END_DATE) VALUES ('10 1234 5678 901');
INSERT INTO BU_REF_NO (END_DATE) VALUES ('12 3456 7890 123');
INSERT INTO BU_REF_NO (END_DATE) VALUES ('123456 7890 123');
INSERT INTO BU_REF_NO (END_DATE) VALUES ('987654 3210 321');
INSERT INTO BU_REF_NO (END_DATE) VALUES ('12345678 1234567890123');
INSERT INTO BU_REF_NO (END_DATE) VALUES ('1234567890123 12345678');
INSERT INTO BU_REF_NO (END_DATE) VALUES ('1234567890 123');
UPDATE BU_REF_NO SET END_DATE = REPLACE(END_DATE,' ','');
SELECT * FROM BU_REF_NO;


END_DATE


12103501

1012345678901

1234567890123

1234567890123

9876543210321

123456781234567890123

123456789012312345678

1234567890123