Purposes and results: In order to, so as to and etc

an action;
Ex.: He took a course in order to get

a better job.
In spoken English in particular it is much more common simply to use a to-infinitive without ‘in order/so as’ to express the same meaning;
Ex.: He took a course to get a better job.

instead of not+to-infinitive;
Ex.: I wrote down her name so as

not to forget it.
In contrastive sentences we can use not+to-infinitive, but+to-infinitive
Ex.: I came to see you not (in order/so as) to complain, but (in order/so as) to apologise.

! We can put in order/so ass before the to-infinitive in sentences like this.

‘So that’ is more common than ‘in order that’, it

is used in less formal situations;
We can leave out ‘that’ after ‘so’, but we always include it after ‘in order’.
Ex.: a) She stayed at work late in order/so as to compare the report.
b) She stayed at work late in order that/so that she could complete the report.

present tense verb in the main clause is usually followed

by a present tense verb (or a modal with present or future reference – can, will, etc.)
A past tense verb in the main clause is usually followed by a past tense verb (or a modal with past reference – could, would, etc.)
Ex.: I hid the presents so that Marie wouldn’t find them.

that’ is used in formal contexts (academic writing) to introduce

a result;
Ex.: The model was designed such that the value of x would be calculated.
‘In such a way that/in such a way as+to-inf.’ we use in less formal contexts with a similar meaning;
Ex.: Our business is managed in such a way as to minimise its environmental impact.

to introduce a result:
Ex.: It is such a popular play

that all the performances were sold out after the first day.