I have a value in my database with comma separated data eg.
11,223,343,123
I want to get the data, if it match a certain number (in this example it's number 223).
WHERE wp_postmeta.meta_value IN
('223', '223,%', '%,223,%', '%,223')
I thought I could use wildcard for it, but with no luck. Any ideas of how to do this? Maybe it's better to do this using PHP?
Storing stuff in a comma separated list usually is a bad idea, but if you must, use the FIND_IN_SET(str,strlist) function.
WHERE FIND_IN_SET('223',wp_postmeta.meta_value)
If you can change your database and normalise it, you would get faster results. Create an extra table that links meta_values to your primary_id in your table.
The wp_post_meta table is designed to hold loads of values, and for that simple reason (and because of database normalization, you should not never comma seperated lists as values in databases.
If you absolutely must use it this way, there are some mySQL functions, one being FIND_IN_SET.
Related
I have a column that has brand names in an array format as below:
I want to extract information associated with Brand4 for example 'price'.
I tried using the below, but that's a psql query. How can I extract this information using MySQL in GCP.
SELECT Brand_name, price
FROM table_name
Where 'Brand4'=Any(Brand_name)
First, the explanation for your error message is that in MySQL, ANY() accepts a subquery, not just a single column or expression. See https://dev.mysql.com/doc/refman/8.0/en/any-in-some-subqueries.html
MySQL does not have an array type. Your Brand_name column is not an array, it's a string. It happens to contain commas and square brackets, but these are just characters in a string.
So your solutions are to use various string-search functions or expressions, as other folks have suggested.
The downside to all the string-search functions is that they cannot be optimized with a conventional index. So every search will be expensive, because it requires a table-scan.
Another solution I did not see yet is to use a fulltext index.
alter table brands add fulltext index (brand_name);
select * from brands
where match(brand_name) against ('Brand4' in boolean mode);
This may require some special handling if the brand names contain spaces or punctuation, but if they are plain words, it should work.
Read https://dev.mysql.com/doc/refman/8.0/en/fulltext-search.html to understand more about fulltext indexes.
The best solution would be to eliminate this fake "array" column by normalizing the schema to store one brand per row in another table. Then you can match strings exactly and optimize with a conventional index. But I understand you said that the table structure is not up to you.
This should work in MySQL (using a string function as mention here):
SELECT *
FROM brands
WHERE FIND_IN_SET('Brand4',brand_name);
see: DBFIDDLE
Provided SQL query will work in MySQL, if you will make a subquery within the parentheses, or use FIND_IN_SET instead of using ANY.
But, as stated in the MySQL documentation:
This function does not work properly if the first argument contains a
comma (,) character.
So, as an alternative, you could use LIKE (simple pattern matching).
Your SQL code then would be:
SELECT `brand_name`, `price`
FROM `test`
WHERE `brand_name` LIKE "%Brand4%"
See SQLFiddle for live example.
Also, you could use LOCATE.
Or any other alternative solution.
But, I must say that storing list data in the way you do, - it's not the best practice out there.
There are plenty of ways this can be done better.
For example, using M:M (many-to-many) relationship.
In case you made this design you really have to reconsider/redesign. Databases have there own data structures and sql is not an imparative language but a declaritve one.
If when you didn´t desing you should consider create a table out of the one column. Perhaps this is what you try.
If it is just locating a specific string in the values of a field use like
SELECT Brand_name, price
FROM table_name
Where brand_anme like '%Brand4%'
But realize this is will not always yield accurate results.
I am working on a project that uses PHP/MYSQL as the backend for an IOS app that makes a lot of use of dictionaries and arrays containing text or strings.
I need to store this text in MYSQL (coming from Arrays of srtrings on phone) and then query to see the text contains (case insensitive) a word or phrase in question.
For example, if the array consists of {Ford, Chevy, Toyota, BMW, Buick}, I might want to query it to see it contains Saab.
I know storing arrays in a field is not MYSQL friendly as it prevents optimization. However, it would be way too complicated to create individual tables for these collections of words which are created by users.
So I'm looking for a reasonable way to store them, perhaps delimited with spaces or with commas that makes possible reasonably efficient searches.
If they are stored separated by spaces, I gather you can do something with regex like:
SELECT
*
FROM
`wordgroups`
WHERE
wordgroup regexp '(^|[[:space:]])BLA([[:space:]]|$)';
But this seems funky.
Is there a better way to do this? Thanks for any insights
Consider using a FULLTEXT index. And use MATCH(...) AGAINST(... IN NATURAL LANGUAGE MODE).
FULLTEXT is very fast for "words", and IN NATURAL MODE may solve your Saab example.
Using regexp can achieve what you want, however, your query will be inefficient, since it cannot rely on any indexes.
If you want to store a list of words and their position within the array does not matter, then you may consider storing them in a single field, space delimited. But instead of using a regexp, use fulltext indexing and searching. This method has a clear advantage over searching with regexp: it uses an index. It has some drawbacks as well: there is a stopword list (these are excluded from searching) and there is a minimum word length as well. The good news is that these parameters are configurable. Also, you get all the drawbacks of storing data in a delimited field, as detailed in Is storing a delimited list in a database column really that bad? question here on SO.
However, if you want to use dictionaries (key - value pairs) or the position within the list may be important, then the above data structure will not do.
In this case, I would consider if mysql is the right choice for storing my data in the first place. If you have multi-dimensional lists, or lists containing lists, then I would definitely choose a different nosql solution.
If you only need simple, two-dimensional lists / dictionaries, then you can store all of them in a single table with a similar structure as below:
list_id - unique identifier of the list, primary key
user_id - id of the user the list belongs to
key - for dictionaries this is the lookup field (indexed), for other lists it may store the position of the element. String data type.
value - the field holding the value (indexed). Data type should be string, so that it could hold different data types as well.
A search to determine if a list holds a certain value would be fast and efficient lookup using the index on either the key or value fields.
I have few fields in one table which are storing comma separated values. I can show query using like or FIND_IN_SET to find data from comma separated values.
MySQL query finding values in a comma separated string
However, I would like to know that how much both options FIND_IN_SET('red',colors) & like with comma giving performance impact? Are they used field indexing to provide result?
If not then how can we optimize query and fetch data fast from comma separated fields using index?
A basic rule in query performance: Have a suitable index tuned for the query. What is your query? Let's also see SHOW CREATE TABLE.
A basic rule in index usage: Don't hide an indexed column inside a function. Doing so leads to ignoring the index. That leads to scanning the entire table. That is slow. I am referring to color hidden in FIND_IN_SET().
A basic rule in building a schema is that "arrays" need to be represented as rows, usually in a separate table. Not in a commalist. Not splayed across columns.
I suspect this may not be doable, but I figured I'd try anyway.
In a MySQL database, one of the columns related is a comma-separated list of values: bob,sally,james,rick.
For a given row, the number of items in this column is variable.
Now, if I want to do a soundex search against all the items in that column (client request well after this db has been established and integrated), how would I go about this? I'd want to write something like
SELECT `primary` FROM `table` WHERE `related`.split(",").any() SOUNDS LIKE sample
Which is plainly nonsense code but hopefully conveys the idea.
Essentially, explode/split a CSV field into individual values to SOUNDEX compare. If I have to get all those related fields, explode them and then soundex() them individually in a PHP foreach() loop so be it (that language isn't really important, it could be Python, too, with just a touch more effort), but I'd love to avoid it if possible.
My knowledge of relational databases is more limited, but is there a SQL command that can be used to create a column that contains a set in each row?
I am trying to create a table with 2 columns. 1 for specific IDs and a 2nd for sets that correspond to these IDs.
I read about
http://dev.mysql.com/doc/refman/5.1/en/set.html
However, the set data type requires that you know what items may be in your set. However, I just want there to be a variable-number list of items that don't repeat.
It would be much better to create that list of items as multiple rows in a second table. Then you could have as many items in the list you want, you could sort them, search for a specific item, make sure they're unique, etc.
See also my answer to Is storing a delimited list in a database column really that bad?
No, there's no MySQL data type for arbitrary sets. You can use a string containing a comma-delimited list; there are functions like FIND_IN_SET() that will operate on such values.
But this is poor database design. If you have an open-ended list, you should store it in a table with one row per value. This will allow them to be indexed, making searching faster.
MySQL doesn't support arrays, lists or other data structures like that. It does however support strings so use that and FIND_IN_SET() function:
http://dev.mysql.com/doc/refman/5.7/en/string-functions.html#function_find-in-set
"SET" data type won't be a good choice here.
You can use the "VARCHAR" and store the values in CSV format. You handle them at application level.
Example: INSERT into my_table(id, myset) values(1, "3,4,7");