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Data cleaning: Difference between revisions
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→check if field value was not fulfilled: NULL, empty value
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([http://sqlfiddle.com/#!2/9b01e/3/0 demo on sqlfiddle]) | ([http://sqlfiddle.com/#!2/9b01e/3/0 demo on sqlfiddle]) | ||
# {{kbd | key = NULL}} value: {{kbd | key = SELECT * FROM table_name WHERE column_name IS NULL;}} | # {{kbd | key = NULL}} value: | ||
# empty value: {{kbd | key = SELECT * FROM table_name WHERE LENGTH(TRIM( column_name )) = 0;}} | #* solution: {{kbd | key = SELECT * FROM table_name WHERE column_name IS NULL;}} | ||
# Excel starting date: 1900/1/0 (converted time formatted value from 0), 1900/1/1 (converted time formatted value from 1), 1900/1/2 ... | # empty value: | ||
#* solution1: {{kbd | key = SELECT * FROM table_name WHERE LENGTH(TRIM( column_name )) = 0;}} | |||
#* solution2: SQL query with the condition {{kbd | key =SELECT * FROM table_name WHERE column_name IS NOT NULL}} includes NULL & empty value {{Gd}} | |||
# Excel starting date: 1900/1/0 (converted time formatted value from 0), 1900/1/1 (converted time formatted value from 1), 1900/1/2 ... | |||
#* solution: step1: Replace the year > 100 from this year with empty value at EXCEL: {{kbd | key =<nowiki>=IF(ISERR(YEAR(A2)), "", IF(YEAR(A2)<1914, "", A2))</nowiki>}} (this formula also handle empty value and non well-formatted column value ex: 0000-12-31 ) ; step2: change the format of cell to time format | |||
== check if field contains value == | == check if field contains value == | ||