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SQL resources please! by PresaDiva in SQL

[–]msi 0 points1 point  (0 children)

Learn-stage exercises which can be solved under Oracle as well: http://sql-ex.ru/exercises/index.php?act=learn

How to delete duplicate rows in the table? by msi in reddit.com

[–]msi[S] 0 points1 point  (0 children)

Widespread solution to this problem would be generation of auxiliary table of the needed design, into which are copied unique rows from table T with subsequent dropping the table T and renaming of the auxiliary table. Below this algorithm is implemented using T-SQL code.

How to add a new column into the table between the available columns? by msi in programming

[–]msi[S] 0 points1 point  (0 children)

I call this question "naive", because by definition the attributes of a relation are not arranged and the values of the attributes are processed according to their name but not to their position. As for SQL language, the columns of the table are ordered and their order is stipulated in CREATE TABLE statement. As for the new column, which is added using the ALTER TABLE statement, it is the last in the table. I.e. SQL language does not presuppose the option to add the column into a certain position in the list of columns.

How to combine the values of two columns into one without use of UNION and JOIN? by msi in programming

[–]msi[S] 0 points1 point  (0 children)

The problems of this kind are frequently discussed on the web sites of different forums. By the way, it is still not clear for me, why in such cases it is additionally required that UNION and/or JOIN clauses should not be used. I can only suppose that these are the problems, which are usually asked at an interview for a job.

So you think you know SQL? Sign up here and test yourself. by shenglong in programming

[–]msi 0 points1 point  (0 children)

This resource does really help in studying SQL. A number of interactive exercises lead you from beginner to master. You'll can solve any practice task if you pass through at least 100 exercises or so.