Zend/Db/Sql/Select - implements multiple combine statements

[turrsis]

No description provided.

[samsonasik]

@return self

[ralphschindler]

There's a lot going on in this PR to have so few details, is this a bug or a feature? And, if a bug, what is it attempting to solve?

[turrsis]

This PR is allow :

SELECT ... UNION SELECT ... UNION SELECT ... UNION SELECT ... UNION SELECT ...

Current implementation allow only one UNION

[ralphschindler]

Well, Postgresql does not support more than 2 sub-selects from being combined. That is one reason why Select was architected in the way it was.

Mainly though, from the perspective of the API, all of the other methods talk about modifying the state of a particular Select, then allow the merging to an external separate Select. I think a way of building a Multi-UNION Select would be to create a new class called SelectUnion/SelectCombined, where the only api is SelectCombine->addSelect(Select $select, $mode); (with additional methods like perhaps union, unionAll, intersect, minus, etc).

So basically, the new API would encourage this:

$selectA = new Select()->from()->where();
$selectB = new Select()->from()->where();
$selectUnion = new SelectCombine('UNION');
$selectUnion->addSelect($selectA)->addSelect($selectB);

instead of this:

$selectA = new Select()->from()->where();
$selectB = new Select()->from()->where();
$selectA->combine($selectB);

Thoughts?

[turrsis]

Good idea, but :

$selectA = new Select();
if ('rainy weather') {
   $selectA->combine(new Select());
}
$selectA instanceof Select === true // and this is good!

But your idea is good because we can simply auto order columns for order.

[ralphschindler]

I agree, $selectCombine instanceof Select should be true.
Another note, what are these NULLable columns, what does that have to do with combining sql statements?

[turrsis]

For UNION statement columns should be ordered for all Select statements.
Very offen situation - column exist in one Select and absent in other, for resolve this we should use NULL columns.
We can use Expression for this, but the code will be unreadable.
For this added NULLable columns

[samsonasik]

remove this @param string $type, not at the function parameter.

[weierophinney]

@ralphschindler where does this stand in regards to milestone? 2.2.6? 2.3.0? later?

[weierophinney]

@turrsis This is looking reasonable. Can you please add docblocks to all class methods? Once that's done, I can merge.

[turrsis]

@weierophinney docblocks added

[turrsis]

@weierophinney Can you merge this (docblocks added)?

[Ocramius]

This feature needs documentation: opened an issue for that.

[Ocramius]

Manually merged in 82504c2

Thanks!