Search results
21 sie 2010 · I'm having a problem where when I try to select the rows that have a NULL for a certain column, it returns an empty set. However, when I look at the table in phpMyAdmin, it says null for most of the rows. My query looks something like this: SELECT pid FROM planets WHERE userid = NULL Empty set every time.
18 mar 2014 · Notice the > '' part, which will check if the value is not null, and if the value isn't just whitespace or blank. Basically, if the field has something in it other than whitespace or NULL, it is true.
I tried the following: SELECT column_name. FROM information_schema.columns. WHERE table_name = "table_name". AND EXISTS (. SELECT DISTINCT column_name FROM table_name WHERE column_name IS NOT NULL. ) But this also returns the column names where all the entries are NULL.
6 cze 2024 · We can use the function NULLIF to compare and check if the column contains null or empty values: SELECT id, name FROM Department WHERE NULLIF(TRIM(code), '') IS NULL; The NULLIF function evaluates its two arguments, returning NULL if they are equal.
An expression that contains NULL always produces a NULL value unless otherwise indicated in the documentation for the operators and functions involved in the expression. All columns in the following example return NULL: mysql> SELECT NULL, 1+NULL, CONCAT('Invisible',NULL);
4 sty 2011 · NULL means absence of value (i.e. there is no value), while empty string means there is a string value of zero length. For example, say you have a table to store a person' data and it contains a Gender column.
In this article, we would like to show you how to find rows where the column value is an empty string in MySQL. Quick solution: SELECT * FROM `table_name` WHERE `column_name` = ''; If your column is NULL then the below query works: SELECT * FROM `table_name` WHERE `column_name` IS NULL; Practical example
