14,970
edits
Data cleaning: Difference between revisions
Jump to navigation
Jump to search
→check if field value was not fulfilled: NULL, empty value
m (→duplicate data) |
|||
| Line 116: | Line 116: | ||
# find records with empty value: (not contains {{kbd | key = NULL}} value) | # find records with empty value: (not contains {{kbd | key = NULL}} value) | ||
#* MySQL: {{kbd | key = SELECT * FROM table_name WHERE LENGTH(TRIM( column_name )) = 0;}} {{Exclaim}} SQL query {{kbd | key =SELECT * FROM table_name WHERE column_name IS NOT NULL}} includes empty value | #* MySQL: {{kbd | key = SELECT * FROM table_name WHERE LENGTH(TRIM( column_name )) = 0;}} {{Exclaim}} SQL query {{kbd | key =SELECT * FROM table_name WHERE column_name IS NOT NULL}} includes empty value | ||
#* MS SQL Server: {{kbd | key = SELECT * FROM table_name WHERE LEN( LTRIM(RTRIM(column_name)) ) = 0;}} <ref>[http://www.1keydata.com/tw/sql/sql-trim.html SQL TRIM 函數 - 1Keydata SQL 語法教學]</ref> | |||
# Excel starting date: 1900/1/0 (converted time formatted value from 0), 1900/1/1 (converted time formatted value from 1), 1900/1/2 ... | # 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 | #* 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 | ||