SELECT

Retrieves data from the tables in the database.

select.png

 

 

Usage

Embedded/Interactive/Module/ODBC/Procedural/JDBC.

In ESQL, the SELECT statement may only be used to declare a cursor or as input to a PREPARE statement.

In a procedural usage context, the SELECT statement may only be used to declare a cursor.

In interactive SQL, the SELECT statement is used for interactive data retrieval. See the Mimer SQL User's Manual, Retrieving Data for more details.

Description

SELECT Statements

Simple SELECT statements are built from a select-expression, see The SELECT Expression, optionally followed by a FOR UPDATE OF clause.

SELECT statements are used in embedded SQL (including procedural usage contexts) to define cursors and as the input to dynamic PREPARE statements.

The embedded SELECT statement is syntactically equivalent to the interactive data retrieval SELECT statement. In embedded contexts however, the statement cannot be used to retrieve data directly but must be implemented through a cursor.

The FOR UPDATE Clause

If the SELECT statement defines a cursor intended for UPDATE CURRENT statements, the for-update clause must be specified. If the FOR UPDATE OF version is used, it must include all the columns to be updated.

Each column specified in the for-update-of must belong to the table or view named in the from clause of the SELECT statement, although the columns in FOR UPDATE OF do not need to be specified in the select clause. No column may be named more than once in the for-update-of clause.

Column names in the for-update-of clause may not be qualified by the name of the table or view. They are implicitly qualified by the table reference in the from clause of the select specification.

FOR UPDATE OF may not be specified if the statement defines a read-only result set, see Updatable Result Sets.

Updatable Result Sets

A result set is only updatable if all of the following conditions are true (otherwise the result set is read-only):

the keyword DISTINCT is not specified

there are no set-functions in the SELECT list (AVG, COUNT, MAX, MIN, SUM)

the FROM clause specifies exactly one table reference and that table reference refers either to a base table or an updatable view

the result set is not the product of an explicit INNER or OUTER JOIN

the GROUP BY clause is not included

the HAVING clause is not included

the keyword EXCEPT is not included

the keyword INTERSECT is not included

the keyword UNION is not included

the ORDER BY clause is not included

it is not the result of a call to a result set procedure

The FOR UPDATE clause has been specified.

A cursor which addresses a read-only result table may not be used for DELETE CURRENT or UPDATE CURRENT statements.

The FOR READ ONLY Clause

The FOR READ ONLY clause is optional since SELECT statements by default are read-only.

Examples

SELECT format, category_id

FROM formats

ORDER BY LOWER(format), category_id;

 

SELECT format AS format_name, category

FROM formats

ORDER BY CASE category WHEN 'ROCK' THEN 1

                       WHEN 'JAZZ' THEN 2

                       ELSE 3

         END

OFFSET 10 ROWS FETCH FIRST 5 ROWS ONLY;

 

List all artists and use the FETCH FIRST construction to pick one arbitrary album for each artist.

SELECT a.artist,

      (SELECT p.product

       FROM mimer_store.products AS p

         JOIN mimer_store.items AS i ON p.product_id = i.product_id

         JOIN mimer_store_music.titles AS t ON i.item_id = t.item_id

       WHERE t.artist_id = a.artist_id

       FETCH FIRST 1 ROW ONLY) AS work_sample

FROM mimer_store_music.artists AS a;

 

Find the 10 most common starts of artist names, leading ‘The’ excluded:

SELECT strt, count(*) AS cnt

FROM

(

    SELECT CASE WHEN artist NOT LIKE 'The %' THEN CAST(artist AS nchar(3))

                ELSE SUBSTRING(artist FROM 5 FOR 3)

           END AS strt

    FROM mimer_store_music.artists

) AS a

GROUP BY str

ORDER BY cnt DESC

FETCH FIRST 10 ROWS ONLY;

Standard Compliance

Standard

Compliance

Comments

SQL-2016

Core

Fully compliant.

SQL-2016

Features outside core

Feature F302, “INTERSECT table operator”.

Feature F304, “EXCEPT ALL table operator”.

Feature F851, “<order by clause> in subqueries”.

Feature F855, “Nested <order by clause> in <query expression>”.

Feature F856,” Nested <fetch first clause> in <query expression>”.

Feature F857, “Top-level <fetch first clause> in <query expression>”

Feature F858, “<fetch first clause> in subqueries”.

Feature F860, “dynamic <fetch first row count> in <fetch first clause>”.

Feature F861, “Top-level <result offset clause> in <query expression>”.

Feature F862, “<result offset clause> in subqueries”.

Feature F865, “dynamic <offset row count> in <result offset clause>”.

Feature T551, “Optional keywords for default syntax” support for the keyword DISTINCT.

 

Mimer SQL Extension

Support for host variable in <fetch first clause> and <result offset clause> is a Mimer SQL extension.