How do we query tables in EOS? Specifically like the WHERE clause in SQL Database?

I see examples that uses iterator to find if the record exists, however I don't see it as the right approach specially if we have large sets of data.

I can use get and find for the primary key, but what about for other keys?

1 Answer 1


You can use primary key or index to query the data.

For the query where, the index provide find and lower_bound and upper_bound method, which returns the iterator, if you have more than one rows, just use code like it below:

while(iter != xxx.end()) {

for lower_bound or upper_bound, or

while(iter != xxx.end() && iter->yourdata == yourquery) {

for find.

  • I think the second condition needs to be != aswell. Otherwise the loop will just check the first element and finish then.
    – tmm
    Jul 12, 2018 at 7:02
  • @TeeAttack42 if you use find method, means that you want to get all the same data with your query, so use ==
    – Jimmy Guo
    Jul 12, 2018 at 7:05
  • Yes but the index needs to be build on that value to use find. If you want to query a value the index is not build upon you can't use find and this condition because the loop will be likely to stop after the first element. So maybe the code/answer should get some context.
    – tmm
    Jul 12, 2018 at 7:37
  • I see, so there's really no way for us to avoid the use of iterator for this kind situation? Thanks!
    – Dominic
    Jul 12, 2018 at 7:44

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