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Data cleaning: Difference between revisions
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== is null == | == is null == | ||
Finds whether a variable is NULL | Finds whether a variable is NULL [http://ideone.com/tKv2gQ demo] | ||
* PHP [http://tw2.php.net/is_null is_null] | * PHP [http://tw2.php.net/is_null is_null] | ||
* Google spreadsheet / Excel: | * Google spreadsheet / Excel: | ||
** [https://support.google.com/drive/answer/3093348 ISERR(value)] " value - The value to be verified as an error type other than #N/A." ex: {{kbd | key = #NULL!}} | ** [https://support.google.com/drive/answer/3093348 ISERR(value)] " value - The value to be verified as an error type other than #N/A." ex: {{kbd | key = #NULL!}} | ||
** If the cell value is exactly {{kbd | key = NULL}} not {{kbd | key = #NULL!}}, You may use {{kbd | key = <nowiki>COUNTIF(value, "NULL")</nowiki>}} or {{kbd | key = <nowiki>EXACT(value, "NULL")</nowiki>}} | ** If the cell value is exactly {{kbd | key = NULL}} not {{kbd | key = #NULL!}}, You may use {{kbd | key = <nowiki>COUNTIF(value, "NULL")</nowiki>}} or {{kbd | key = <nowiki>EXACT(value, "NULL")</nowiki>}} | ||
* MySQL SQL syntax: {{kbd | key = SELECT * FROM table WHERE column IS NULL;}}<ref>[http://dev.mysql.com/doc/refman/5.0/en/working-with-null.html MySQL :: MySQL 5.0 Reference Manual :: 3.3.4.6 Working with NULL Values]</ref> | * MySQL SQL syntax: {{kbd | key = SELECT * FROM table WHERE column IS NULL;}}<ref>[http://dev.mysql.com/doc/refman/5.0/en/working-with-null.html MySQL :: MySQL 5.0 Reference Manual :: 3.3.4.6 Working with NULL Values]</ref> | ||
Finds whether a variable is NOT NULL | Finds whether a variable is NOT NULL | ||
* MySQL SQL syntax: {{kbd | key = SELECT * FROM table WHERE column IS NOT NULL;}} | * MySQL SQL syntax: {{kbd | key = SELECT * FROM table WHERE column IS NOT NULL;}} | ||
== check if field value was not fulfilled: NULL, empty value == | == check if field value was not fulfilled: NULL, empty value == | ||