Excel/Open Office date difference

You can get date difference between 2 dates on spreadsheet column by using below formula

=A1-B1

Screenshot

MYSQL - Add specific time/day to given date

UPDATE tablename
SET field2 = date_add(field1,INTERVAL xx DAY);
Example :

UPDATE item_order set duedate = DATE_ADD(dateorder, INTERVAL 30 DAY);

MYSQL - Remove character/blank space in table fields.

UPDATE table_name
SET field_name= REPLACE(field_name,'<character to find>', '<character to replace>');

MYSQL - Join Table

SELECT a.field1,a.field2,b.field3,b.field4
FROM table1 a, table2 b
where a.field1 = b.field3

MYSQL - Insert Select Statement

i use this statement when i want to copy data in selected fields in a table.

INSERT INTO student_subject (subjectid, noofsem)
SELECT subjectid, noofsem FROM study_plan
WHERE student_subject.intakeid = study_plan.intakeid