P粉8264299072023-08-14 15:05:22
First of all, you have to accept the fact that if your query doesn't find any rows, that means there is no match, even if you can swear that the data is correct. When a query returns no rows, no rows match the criteria. So you have to find out why. But first you need to make sure your query is correct:
First you need to make sure your query actually has no errors, as "no results" may mean there is an error in the query. For details, refer to these answers: pdo and mysqli.
Check your conditions. There are some mutually exclusive conditions, such as WHERE col=1 AND col=2
. It never returns any rows. Try simplifying the condition until it starts returning some rows, then refine the condition to get the results you want.
But okay, there are no errors, the conditions are correct and you could swear there is data in the table that matches your query. However, there are still some pitfalls:
First, where a variable is involved, make sure it exists and actually contains some value.
Then check the value itself. There may be some converted or unprintable characters in the input data (or database). For example, newline characters or specially encoded symbols, or some characters such as <
and >
are converted into HTML entities. The result is that a query containing <abc@abcs.com>
will never match the text <abc@abcs.com>
. For a quick check, you can use the rawurlencode()
function, which will convert all non-Latin characters into codes, thus making them visible.
The problem is, this is just a guess, no one can tell you what the actual problem is, because this is your database, your input data, only You can find the problem.
I wrote an article explaining how to debug your PDO issues .
To debug a specific problem, you need:
urlencode()
function will help, it will display all non-printable and converted characters in the database and input. Another common problem is when you have multiple databases and connect to the wrong database, it doesn't have the requested data. This question is similar to this question, so just follow the same steps to check, except instead of checking a list of tables you have rows of data.
This is a rare case, but just to be sure, follow this good answer's checklist.