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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 · If you simply want to check if a column is null or empty, you may be better off doing this: SELECT myCol FROM MyTable WHERE MyCol IS NULL OR MyCol = '' See TRIM COALESCE and IS NULL for more info.
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.
WHERE Syntax. SELECT column1, column2, ... FROM table_name. WHERE condition; Note: The WHERE clause is not only used in. SELECT statements, it is also used in UPDATE, DELETE, etc.!
To filter data by multiple conditions in a WHERE clause, use the AND operator to connect the conditions. Here’s what this looks like for two conditions: WHERE condition1 AND condition2. In our example, condition1 is dept = 'Finance' and condition2 is salary > 4000.
Summary: in this tutorial, you will learn how to use the MySQL WHERE clause in the SELECT statement to filter rows from the result set. Introduction to MySQL WHERE clause. The WHERE clause allows you to specify a search condition for the rows returned by a query. The following shows the syntax of the WHERE clause:
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.
