Data cleaning

is null

Finds whether a variable is NULL

• PHP is_null
• Google spreadsheet:
  • ISERR(value) " value - The value to be verified as an error type other than #N/A." ex: #NULL!
  • If the cell value is exactly NULL not #NULL!, You may use EXACT(value, "NULL")
• MySQL SQL syntax: SELECT * FROM table WHERE column IS NULL; demo

Finds whether a variable is NOT NULL

• MySQL SQL syntax: SELECT * FROM table WHERE column IS NOT NULL; demo

check if field value was not fulfilled: NULL, empty value

1. NULL value: SELECT * FROM table_name WHERE column_name IS NULL;
2. empty value: SELECT * FROM table_name WHERE LENGTH(TRIM( column_name )) = 0;

check if field contains value

(left blank intentionally)