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What is the use of column alias in mysql?
COLUMN ALIASES are used to make column headings in your result set easier to read. TABLE ALIASES are used to shorten your SQL to make it easier to read or when you are performing a self join (ie: listing the same table more than once in the FROM clause).
Can we use column number in ORDER BY clause?
SQL ORDER BY Sorting by column number (instead of name) You can use a column’s number (where the leftmost column is ‘1’) to indicate which column to base the sort on, instead of describing the column by its name.
How to use alias in calculation for another field?
(SELECT COUNT (*) FROM UserEvent UE WHERE UE.EventTypeID = 1 AND UE.PracticeID = au.PracticeID AND (UE.EventDate BETWEEN @Date1 and @Date2) – COUNT (CASE WHEN udi.DevicePlatform = ‘iOS’ THEN 1 ELSE NULL END) + COUNT (CASE WHEN udi.DevicePlatform = ‘Android’ THEN 1 ELSE NULL END) Desktop Logics 2.)
Can you use column alias in the same select list?
Documentation do not guarantee the calculations order, but in practice all calculations are performed from left to right. You cannot use an alias in the same SELECT list. Replace alias with the computed columns. Thanks for contributing an answer to Database Administrators Stack Exchange!
Can You reuse an alias in a derived query?
Aliases can only be referenced again at certain points (particularly in GROUP BY and HAVING clauses). But you can’t reuse an alias in the SELECT clause. So you can use a derived query (such as suggested by Rubens Farias) which lets you basically rename your columns and/or name any computed columns.
How to use an alias in MySQL calculations?
My calculations are much more complicated and thats why it would be nice to alias it since I repeat it several times different ways. Simply wrap your reused alias with (SELECT alias) : Aliases in sql are not like variables in a programming language.