Vertica Analytics Platform Version 10.1.x Documentation

SELECT

Returns a result set from one or more data sources—tables, views, joined tables, and named subqueries.

Syntax

[ AT epoch ] [ WITH-clause ] SELECT [ /*+ LABEL(label-name)*/ ] [ ALL | DISTINCT ] 
    { * | expression [ [AS] alias ] }[,…]
    [ into-table-clause ]
    [ from-clause ]
    [ where-clause ]
    [ time-series-clause ]
    [ group-by-clause[,…] ]
    [ having-clause[,…] ]
    [ match-clause ]
    [ union-clause ]
    [ intersect-clause ]
    [ except-clause ]
    [ order-by-clause [ offset-clause ]]
    [ limit-clause ]
    [ FOR UPDATE [ OF table-name[,…] ] ]

Parameters

SELECT clauses such as INTO and WHERE are discussed on separate pages.

AT epoch

Returns data from the specified epoch, where epoch is one of the following:

  • EPOCH LATEST: Return data up to but not including the current epoch. The result set includes data from the latest committed DML transaction.
  • EPOCH integer: Return data up to and including the integer-specified epoch.
  • TIME 'timestamp': Return data from the timestamp-specified epoch.

These options are ignored if used to query temporary or external tables.

See Epochs for additional information about how Vertica uses epochs.

For details, see Historical Queries.

WITH-clause

Defines one or more named common table expressions (CTEs). Each CTE encapsulates a result set that can be referenced by another CTE in the same WITH clause, or by the primary query of the WITH clause.

For details, see WITH Clause.

/*+LABEL(label-name)*/

Assigns a label to a query so you can identify it for profiling and debugging.

In a UNION statement, only the first SELECT statement can be labeled; Vertica ignores labels in subsequent SELECT statements.

ALL | DISTINCT
  • ALL (default): Retains duplicate rows in result set or group.
  • DISTINCT: Removes duplicate rows from the result set or group.

The ALL or DISTINCT qualifier must immediately follow the SELECT keyword. Only one instance of this keyword can appear in the select list.

*

Lists all columns in the queried tables.

Selecting all columns from the queried tables can produce a very large wide set, which can adversely affect performance.

expression [[AS] alias]

An expression that typically resolves to column data from the queried tables—for example, names of columns that are specified in the FROM clause; also:

You can optionally assign a temporary alias to each column expression and reference that alias elsewhere in the SELECT statement—for example, in the query predicate or ORDER BY clause. Vertica uses the alias as the column heading in query output.

FOR UPDATE

Specifies to obtain an X lock on all tables specified in the query, most often used from READ COMMITTED isolation.

FOR UPDATE requires update/delete permissions on the queried tables and cannot be issued from a read-only transaction.

Privileges

Non-superusers:

  • USAGE on the schema
  • SELECT on the table or view

As view owner, you can grant other users SELECT privilege on the view only if one of the following is true:

  • You own the view's base table.
  • You have SELECT...WITH GRANT OPTION privilege on the view's base table.

Example

When multiple clients run transactions as in the following example query, deadlocks can occur if FOR UPDATE is not used. Two transactions acquire an S lock, and when both attempt to upgrade to an X lock, they encounter deadlocks:

=> SELECT balance FROM accounts WHERE account_id=3476 FOR UPDATE;
    …
=> UPDATE accounts SET balance = balance+10 WHERE account_id=3476; 
=> COMMIT;