"GNR" is a string column and I expect the filter expression "GNR"='.11' to only return the feature with the value '0.11'.
Why are the other features with values of '.110'and '.1100' included?
Is there something wrong with my query?
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What if the column GNR was column of strings and that we only wanted to filter the strings that contained a certain sequence of characters? For example the string "(historical)" that ends certain strings in the list. So there is no perfect equal. – user53059 Jun 2 '15 at 11:38
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1Easy: "NAME"LIKE'%(historical)%' – user53059 Jun 2 '15 at 11:44
There is nothing wrong with your query.
= is a comparison operator and it returns all the records which begins with your string
Use this instead:
"GNR" LIKE '.11'
When you compare alphabetic characters, use ILIKE instead.
EDIT
In QGIS 2.0.1 or newer you can use regular expressions, also:
regexp_match("GNR", '^.11$')
where:
^indicates the start of the string;$indicates the end of the string.
answered Jan 28 '14 at 11:24
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Thanks. That did the trick. For me, coming from an SQL background, 'LIKE' and '=' act just the other way round. – Wilhelm Berg Jan 28 '14 at 13:24
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1
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Ok. This bug/implementation detail. QgsExpression will try and convert both sides to a double and compare that for faster results. – Nathan W Jan 28 '14 at 23:33
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1You can also do this:
"GNR" ~ '^.11$'which is a regex match and will force a string. – Nathan W Jan 28 '14 at 23:34 -
Nathan did great observations! Therefore, due to the perfect compatibility with the older QGIS versions (tested on 1.8 and 1.7), "GNR" ~ '^.11$' is the way to go when you need equality! – Sorin Călinică Jan 29 '14 at 11:21
