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18 mar 2014 · In MySQL, can I select columns only where something exists? For example, I have the following query: select phone, phone2 from jewishyellow.users where phone like '813%' and phone2
29 lis 2019 · the NULLIF checks fieldname for the empty value and would convert to NULL if it was empty. The ISNULL returns 1 (true) if the NULLIF succesfully changed an empty field to NULL or if it was already NULL....
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.
6 cze 2024 · The IS NULL operator checks whether the column contains null values. To detect empty values within the column, we compare it against the empty string (”). Sometimes, a column might contain values that consist only of spaces, especially when data is imported from various sources.
30 lis 2013 · I need to find out the records where the article_title data is the same on more than one record. Here's what I've got: select a.* from articles a where a.article_title = (select article_title from articles where article_title = a.article_title AND a.id <> articles.id)
2 lut 2024 · To ascertain if a column is empty or null in SQL, use COALESCE (column, ”) or column IS NULL OR column = ”. These queries fetch rows where the specified column contains an empty string or null value, ensuring comprehensive coverage of both scenarios.
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.
