Postgresql流水帐(第六天):view

CREATE OR REPLACE view_name

AS

query

DROP VIEW [ IF EXISTS ] view_name;

一个复杂的 query:

SELECT cu.customer_id AS id,

    (((cu.first_name)::text || ' '::text) || (cu.last_name)::text) AS name,

    a.address,

    a.postal_code AS "zip code",

    a.phone,

    city.city,

    country.country,

        CASE

            WHEN cu.activebool THEN 'active'::text

            ELSE ''::text

        END AS notes,

    cu.store_id AS sid

   FROM (((customer cu

     JOIN address a ON ((cu.address_id = a.address_id)))

     JOIN city ON ((a.city_id = city.city_id)))

     JOIN country ON ((city.country_id = country.country_id)));

 

将复杂的 query 存储为 view:

CREATE VIEW customer_master AS

SELECT cu.customer_id AS id,

    (((cu.first_name)::text || ' '::text) || (cu.last_name)::text) AS name,

    a.address,

    a.postal_code AS "zip code",

    a.phone,

    city.city,

    country.country,

        CASE

            WHEN cu.activebool THEN 'active'::text

            ELSE ''::text

        END AS notes,

    cu.store_id AS sid

   FROM (((customer cu

     JOIN address a ON ((cu.address_id = a.address_id)))

     JOIN city ON ((a.city_id = city.city_id)))

     JOIN country ON ((city.country_id = country.country_id)));

 

A PostgreSQL view is updatable when it meets the following conditions:

• The defining query of the view must has exactly one entry in the FROM clause, which can be a table or another updatable view.
• The defining query must not contain one of the following clauses at top level: GROUP BY,HAVING, LIMIT, OFFSET, DISTINCT, WITH, UNION, INTERSECT, and EXCEPT.
• The selection list must not contain any window function or set-returning function or any aggregate function such as SUM, COUNT, AVG, MIN, MAX, etc.

 

CREATE VIEW usa_cities AS SELECT

city,

country_id

FROM

city

WHERE

country_id = 103;

 

 

PostgreSQL Materialized Views

CREATE MATERIALIZED VIEW view_name

AS

query

WITH [NO] DATA;

 

REFRESH MATERIALIZED VIEW view_name;

REFRESH MATERIALIZED VIEW CONCURRENTLY view_name;

When you refresh data for a materialized view, PosgreSQL locks the entire table therefore you cannot query data against it. To avoid this, you can use the CONCURRENTLY option.

1	REFRESH MATERIALIZED VIEW CONCURRENTLY view_name;

With CONCURRENTLY option, PostgreSQL creates a temporary updated version of the materialized view, compares two versions, and performs INSERT and UPDATE only the differences. You can query against the materialized view while it is being updated. One requirement for usingCONCURRENTLY option is that the materialized view must have a UNIQUE index. Notice thatCONCURRENTLY option is only available from PosgreSQL 9.4.