表中的 Select 行以列表中的特定字符串值结尾

Question

I have a table with two columns item_name , value where item_names looks like "abracadabra_prefix.tag_name". And I need to select rows with tag_names from a list that doesn't have a prefix.

Should be somthing like:

tag_names = ['f1', 'k500', '23_g']

SELECT * FROM table WHERE item_name IN (LIKE "%{tag_names});

input table:

item_name	value
fasdaf.f1	1
asdfe.f2	2
eywvs.24_g	2
asdfe.l500	2
asdfe.k500	2
eywvs.23_g	2

output table:

item_name	value
fasdaf.f1	1
asdfe.k500	2
eywvs.23_g	2

I have tried concatenating a string in a loop to get a query like this:

SELECT * FROM table WHERE item_name LIKE '%f1' OR item_name LIKE '%k500' OR item_name LIKE '%23_g';

But I can have from 1 to 200 tags, and with a large number of tags, this makes the query too complicated,as I understand it.

Answer 1

You can use:

• UNNEST to extract tag values from your array,
• CROSS JOIN to associate tag value to each row of your table
• LIKE to make a comparison between your item_name and your tag

SELECT item_name, value_ 
FROM tab
CROSS JOIN UNNEST(ARRAY['f1', 'k500', '23_g']) AS tag
WHERE item_name LIKE '%' || tag || '%'

Output:

item_name	value_
fasdaf.f1	1
asdfe.k500	2
eywvs.23_g	2

Check the demo here .

Answer 2

You can extract the suffix of item_name using substring with regexp and then use the any operator for comparison in the where clause.

select * from the_table
where substring (item_name from '\.(\w+)$') = any('{f1,k500,23_g}'::text[]);

SQL fiddle demo
If you intend to use the query as a parameterized one then it will be convenient to replace '{f1,k500,23_g}'::text[] with string_to_array('f1,k500,23_g', ',') , ie pass the list of suffixes as a comma-separated string. Please note that this query will result in a sequential scan.