I have a large mySQL database and I want to remove every record that is empty, not null in a certain column. What is the best way to do write a SQL query for this?
Currently I have tried:
DELETE FROM Businesses WHERE WEBADDRESS IS NULL
But it did not delete anything. There are 44,000 records and almost 80% of them are null in that column.
DELETE FROM myTable WHERE myColumn IS NULL
Link to MySQL page for DELETE syntax: http://dev.mysql.com/doc/refman/5.7/en/delete.html
IF the column is not NULL but just blank you would need to do something like:
DELETE FROM myTable WHERE myColumn = ''
Based on the information you also provided in the comments, the values are likely being loaded as empty ('') and not NULL: http://dev.mysql.com/doc/refman/5.7/en/problems-with-null.html
The second query should work.
delete from your_table
where certain_column is null
DELETE from `<tablename>`
WHERE `<columnname>` is null
delete from table_name where column=''
delete from table_name where column_name is null;
this query will definitely work for you.
Don't worry about count of data. Mysql can handle it. Just write:
DELETE FROM `Businesses` WHERE `WEBADDRESS` = '';
Related
I am trying to use an update query to update fields from one table to another for fields but only if the fields in the table that i am updating into is blank. If they contain information, I do not want to overwrite the existing data
e.g
Field: Name
Table: Table 1
Update to: [Table2.][Name]
Criteria:
I am unsure of what to put in the criteria. I tried, 'Is Null', Like "".
Here is an example:
UPDATE MyTable SET MyTable.FieldB = "MyNewValue" WHERE (((MyTable.FieldB) Is Null));
Looking at the Query from within Access, you can switch to SQL view. You just need to put Is Null in the criteria column: UPDATE MyTable SET MyTable.FieldB = "MyNewValue" WHERE (((MyTable.FieldB) Is Null));
Furthermore, you can just write Is Null on alternate lines and it will count as OR.
In my SQL tables there are rows where columnX has empty value (""). Now i want them i queried to select them and then delete them.
Query like:
tables has empty rows
Delete empty rows
How can i do this. Any idea
Depending on what exactly you mean by "empty" rows:
delete from yourTable where column1 is null
will delete where column1 has a null value. If you mean where multiple columns have nulls, it's just a matter of adding more conditions to the where clause:
delete from yourTable where column1 is null and column2 is null and column3 is null
If by empty you mean "has spaces in a text field or the field is empty" you can use some of the builtin functions to find them for example:
delete from yourTable where trim(column1)=''
which would find a row in the table where column1 only has white space in it and so on.
You might want to have a read of this article that I wrote on SQL, join and the like - it has got a fair bit in it about selecting the right rows from the table - and in your case, replace the select.... from where... with a delete from where...
Having said all that, I would really wonder why you are inserting data into your table that you don't want in it?
You can check each field for null or the empty string like this:
DELETE FROM table WHERE (column1 IS NULL OR column1 = '') AND (column2 IS NULL OR column2 = '')
Just add the rest of your columns to the WHERE clause.
Simple : delete from Test_table where c1 is null,....and cN is null
Ok Try this, i hope u'll find your solution
What you need is, first get empty rows
Select * From table_name Where column_name = "";
Then Delete the empty rows
Delete From table_name Where column_name = "";
or don't write the select query only write the delete query
I hope this solve your problem
I have a Account-Database with a "last-login" row, I want to delete all accounts which are empty (NULL) at last-login row.
Does someone know a MySQL Query for this? (Database-Structure is like: User-Id, password, last-login)
This should do the the tricks:
DELETE FROM Account-Database WHERE last-login IS NULL;
or if the field is just an empty field (not null but '')
DELETE FROM Account-Database WHERE last-login= '';
See: http://dev.mysql.com/doc/refman/5.0/en/delete.html
delete from Account-Database where `last-login` is NULL;
It's not clear in your question whether Account-Database is the table name or the database name but you get the idea.
<?php
mysql_query("Delete from Account-Database where last-login = NULL");
?>
DELETE FROM `Account-Database` WHERE `last-login` IS NULL;
The syntax for a DELETE query is as follows:
DELETE FROM `tablename` WHERE conditions
Is it possible to update zero columns in a MySQL update query?
I'd like to utilise the automatic updating of the timestamp column when this particular row is selected. Does anyone have any clue?
So you want your update query to only update the timestamp column? Just update it yourself instead of relying on the automatic update:
UPDATE mytable SET tscolumn = NOW() WHERE ...
Just try something like :
UPDATE myTable SET someField = someField WHERE id = myId
So the data values won't move, and the automatic timestamp will be updated.
As said by GaryG, you may also update the timestamp directly.
I've looked all over the internet for my answer, and perhaps I'm just doing things wrong. I have a column in my MySQL table that I need to replace all the NULL values with a text string in my SQL Query using phpMyAdmin. I don't want the output to come out that way, I want to actually replace the null values with the text string.
I've tried
UPDATE `tablename` SET fieldname = replace (fieldname, "", "textstring")
I've read up on
SELECT ISNULL(field,"replacetext)
But this only shows the output, but doesn't actually replace it in the table.
I can't figure this out, and I've wasted so much time trying to find an answer.
update tablename set fieldname = "textstring" where fieldname is null;
Have you tried
UPDATE `tablename` SET fieldname = '' where fieldname is null