在MySQL中删除尾随空格

Question

Why does my SELECT not ignore whitespace, and why does TRIM seem to have no effect?

Here are the partial results of something like SELECT DISTINCT crop_year from raw_data :

Rows    crop_year
105755  '2010'
12326   '2010 '
256363  '2011'
319321  '2011 '
...

I typed in the single quotes to illustrate the fact that there is trailing whitespace.

I have 2 problems here on my production server... which I cannot replicate locally:

A. I expect SELECT to ignore whitespace, as explained in numerous other questions, as well as the MySQL Docs , but it clearly does not work this way on my prod server.

B. I expect UPDATE raw_data SET crop_year = TRIM(crop_year) to fix the problem, but running this query results in 0 affected rows.

Other background: This column type is VARCHAR(11). If it's relevant, the table contains mixed storage engines and collations: this table is MyISAM, and this column is currently latin1_swedish_ci.

PS: In this specific case, year is always a 4 digit value, so I eventually changed the column from a VARCHAR(11) to CHAR(4)... which effectively trimmed the whitespace, but I am still posting the question because I find it likely that I will encounter a similar problem on other columns which are not of a fixed length.

Answer 1

Figured it out, with help from this question . TRIM does not respect all whitespace... just spaces. In my case, I needed:

select distinct trim(BOTH '\\r' from crop_year) as crop_year FROM raw_field_data

Other variations could include

select distinct trim(BOTH '\\n' from crop_year) as crop_year FROM raw_field_data or select distinct trim(BOTH '\\n\\r' from crop_year) as crop_year FROM raw_field_data

Answer 2

Maybe you place extra space in your "form" when you enter the value on the crop year. check your input forms maybe...