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Column alias in where clause postgresql

You ask two questions: 1. Why can't I refer to the SELECT cost alias at the WHERE clause? 2. But why order by cost desc; is allowed?. A PostgreSQL alias assigns a table or a column a temporary name in a query. you can assign an alias to an expression in the SELECT clause as follows. "Ron ywypugivupid.tk" writes: > I'm using a query with similar functionality to the following: > SELECT id, > sum(hours) AS totalhours.

I'm a little confused about how to use a column alias in the where clause of a query. I'm sure the answer is something simple, but I haven't. Postgres doesn't seem to allow me to use a column alias as an identifier in a WHERE clause, but this is so inconvenient I feel I must be doing. It's inconvenient sometimes, but it's SQL standard behavior, and it prevents ambiguities. You cannot reference column aliases in the same.

The column aliases there override the column names/aliases of the internal select subquery (derived table). The same way, they can override. WHERE and HAVING are resolved before column aliases are Aside: the subquery in your example is just noise since the WHERE clause is. You can't reference an alias on the same "level" where it was defined. You need to wrap your base query into a derived table: select * from. PostgreSQL ALIAS Syntax - Learn PostgreSQL in simple and easy steps starting from Constraints, Joins, Unions Clause, NULL Values, Alias Syntax, Triggers, The column aliases are used to rename a table's columns for the purpose of a . By the way, can't we just always quote all the identifiers (i.e. table names, column names, aliases, etc)? I think this will prevent such problems in.

You can only reference xy if it were a CTE. The reason is because it's born at the same time as you main query. So for reference you'd have to. PostgreSQL ALIASES can be used to create a temporary name for columns or a self join (ie: listing the same table more than once in the FROM clause). If you want to use an alias in the WHERE clause you have to introduce it in the FROM clause, such as: SELECT * FROM mytable AS myalias (xx. They can be used for the target columns of your SELECT clauses, even if Notice the subquery recognized the hs table ALIAS from the outer.

It is hardly known, how to alias the columns of the table. But chances are you don't know how to alias the column names of a table in the from clause. DB PostgreSQL 1 SQL Server 2 3 SQLite accepts prior to table alias from clause. The DISTINCT clause specifies a column (or expression) for which to retrieve . The FROM sources which have assigned aliases may also alias columns by. SQL is a language with many unique aspects. One of those is the fact that the logical order in which the various query clauses are evaluated is. If the LIMIT (or FETCH FIRST) or OFFSET clause is specified, the SELECT statement only If an alias is written, a column alias list can also be written to provide.

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