DBAL基数违规错误

Question

I am getting the 'Cardinality Violation' error, for the following SQL:

Doctrine\\DBAL\\Exception\\DriverException: An exception occurred while executing

SELECT p.* FROM mod_products_products p 
LEFT JOIN mod_products_products_categories c_link ON c_link.product_id = p.id 
LEFT JOIN mod_products_brands b ON p.brand_id = b.id 
LEFT JOIN mod_products_groups vg ON p.variation_id = vg.id 
LEFT JOIN mod_products_categories c ON c_link.category_id = c.id 
LEFT JOIN mod_products_group_options vg_o ON vg_o.group_id = vg.id 
LEFT JOIN mod_products_group_values vg_o_v ON vg_o_v.option_id = vg_o.id 
WHERE (p.name LIKE (?, ?)) AND (p.parent_id = 0) AND (vg_o.disabled=0) 
GROUP BY p.id ORDER BY p.name ASC 
LIMIT 18446744073709551615 OFFSET 0

with params ["%big%", "%light%"]: SQLSTATE[21000]: Cardinality violation: 1241 Operand should contain 1 column(s).

The error only occurs if there is more than one value defined in the parameter list for WHERE (p.name LIKE (?, ?)) .

I am using executeQuery() , and passing the array as Connection::PARAM_STR_ARRAY . In the original statement I am defining the trouble point as:

$builder->andWhere('p.name LIKE (:partial_names)');

It seems it doesn't like getting an array passed as partial_names. Any ideas on what is causing this, and how to avoid it?

Answer 1

MySQL LIKE is a "string comparison function" and as such compares one string to another, using "simple pattern matching".

If you check the SQL standard , you'll notice that the BNF grammar for LIKE accepts only "character-like" and "octet-like" arguments, both of which are essentially what we'd call strings. (There is some detail around the fact that LIKE performs a binary, character-for-character match on the RHS, which is different than how = operates: foo LIKE 'bar' and foo='bar' may produce different results.)

All this means you can't do LIKE ('a', 'b') because the columnar expression ('a', 'b') is not string-like. Or in geeky standard language, it's cardinality (2) differs from the expected cardinality (1). However, you can do this in MySQL and SQLite (maybe other engines):

WHERE foo LIKE ('%bar')

because the cardinality of the RHS is 1 (there is one column), which is what LIKE expects.

You're wanting something effectively similar to foo LIKE IN ('a', 'b') , but that doesn't exist either (for the SQL standard reason mentioned above). This Q&A shows some workarounds for that behavior, REGEXP based being the accepted answer.

So, to get around this error, you need to rewrite your query to use multiple LIKE , or a REGEXP , or maybe even something like FIND_IN_SET .

Answer 2

Change

(p.name LIKE (?, ?))

to

(p.name LIKE ? OR p.name LIKE ?)

and

["%big%", "%light%"]

to

"%big%", "%light%"