6 ms·
There is a difference. You are right in a sense that scalar expressions are a form of a table expression, but... This is a valid expression: SELECT (SELECT
by RedCrowbar 7y ago
There is a difference. You are right in a sense that scalar expressions are a form of a table expression, but...
This is a valid expression:
SELECT (SELECT count(*) FROM table) + 1
This is not:
SELECT (SELECT * FROM table), 1
In EdgeQL:
SELECT (count(SomeType) + 1)
and
SELECT (SomeType, 1)
are equally valid.
- deleted 7y ago[deleted]
- Svip 7y agoThe brackets make it look like they are both subqueries and contained within in the EdgeQL examples. As such, you could write the examples in SQL like this: SELECT count(*) + 1 FROM table And SELECT *, 1 FROM table Both of which are valid in SQL. And you'd get the same result as in the EdgeQL examples. Indeed, a more relevant second counter example would be: SELECT (SELECT * FROM table) + 1 Not valid... unless `table` only had one row and one column containing a number.
- RedCrowbar 7y agoYes, and that's actually the point being made in the post. You need to rewrite your queries to make SQL happy.
- notimetorelax 7y agoIs this such a common problem that you need a new language to solve it?
- 1st1 7y agoWe think that people struggling with writing good/advanced SQL queries and the existence of ORMs and other heavy frameworks to make RDBMSes "friendly" is a serious problem. And inventing a a new querying language is a necessary step to make relational databases more accessible.
- munk-a 7y agoJust to clarify (and I strongly dislike overuse of ORMs)... Some people use a thing x A subset of those people use a subset of x called y This subset of people have built a tool to make y easier to express Thus x is invalid I think that's a really bad argument, if everyone was using ORMs then we'd all merrily forget about SQL and just use ORMs which would become the new "language for structuring queries", but we don't all, and EdgeDB in particular thinks that ORMs provide a much degraded expression set from SQL and thus want to tweak X so that it's as expressible as the tool to express Y but without making it just about Y... I think your goal boils down to shifting the trade-off point between X and Y - the extreme of which is writing a very expressive Y that also supports X but in a non-expressive manner.
- tathougies 7y agoThe EdgeQL query has no obvious meaning, unless (,) calculates the cross product. Saying SELECT Table1, 1 returns each row of Table1 along with 1 and that 1 returns the set {1} means that you have arbitrarily assigned each row of Table1 a row from the set {1}. This gives what you want in the case of a scalar, but what about a non-scalar. For example, suppose Table1 contains (John, Smith), (Alice, Perkins), (Bob, Best). Then, what should SELECT Table1, {1,2} return? If you do not say cross product, you have arbitrarily assigned rows to one another, resulting in meaningless data. If you say cross product, then you have rewritten the sql expression SELECT * FROM Table1, (VALUES (1), (2)) I don't disagree the SQL syntax is longer and has some unnecessary keywords, but unlike EdgeQL, the query means something particular.
- RedCrowbar 7y agoIn EdgeQL, expressions are element-wise functions over the cross-product of the input sets: edgedb> SELECT {'First', 'Second'} ++ '!'; {'First!', 'Second!'} EdgeQL queries are essentially set comprehensions.
- tathougies 7y agoRight, so SELECT Table1 and SELECT 1 compose to SELECT Table1, 1 in the same way that SELECT 1 and SELECT * FROM TABLE1 and SELECT 1 compose to > SELECT * FROM TABLE1, (SELECT 1) Aside from the different syntax, it is the same kind of composition. Not sure what EdgeQL has gained here, then.
- theclaw 7y agoErm, isn’t the syntax the whole point of this discussion?
- tathougies 7y ago> SELECT (SomeType, 1) This cannot be the case if you call each thing a 'set'. Unless `(a, b)` calculates the cross product, there is no meaningful non-arbitrary way to assign each element of a to an element of b. That would depend on an ordering, which makes it not a set to everyone but a marketing dept somewhere.
- RedCrowbar 7y ago`(a, b)` is a cross-product, just like "SELECT * FROM a, b"
- thwd 7y agoThey're saying that both of those expressions are valid, not equivalent. SELECT count(star) FROM table and SELECT star FROM table Are both valid, not equivalent. Furthermore, listing any kind of set depends on some ordering, be it random.
- tqi 7y ago> SELECT (SELECT * FROM table), 1 What would you expect to returned for by this query?