sql-view | 易学教程

How do MySQL views work?

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问题 When I create a view I am basically making a new table that will automatically be transacted upon when data in one of the tables it joins changes; is that correct? Also why can't I use subqueries in my view? 回答1: A view works like a table , but it is not a table. It never exists; it is only a prepared SQL statement that is run when you reference the view name. IE: CREATE VIEW foo AS SELECT * FROM bar SELECT * FROM foo ...is equivalent to running: SELECT x.* FROM (SELECT * FROM bar) x A

Change PostgreSQL columns used in views

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I would like PostegreSQL to relax a bit. Every time I want to change a column used in a view, it seems I have to drop the view, change the field and then recreate the view. Can I waive the extra protection and just tell PostgreSQL to let me change the field and then figure out the adjustment to the view? Clarification: I understand what a view is. In fact, it's because the view is like a subquery that I wish I could just change the underlying tables and have the view pick up the change. Let's say I have the following: CREATE TABLE monkey ( "name" character varying(50) NOT NULL, ) CREATE OR

Change PostgreSQL columns used in views

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问题 I would like PostegreSQL to relax a bit. Every time I want to change a column used in a view, it seems I have to drop the view, change the field and then recreate the view. Can I waive the extra protection and just tell PostgreSQL to let me change the field and then figure out the adjustment to the view? Clarification: I understand what a view is. In fact, it\'s because the view is like a subquery that I wish I could just change the underlying tables and have the view pick up the change. Let\

Entity Framework and SQL Server View

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问题 For several reasons that I don\'t have the liberty to talk about, we are defining a view on our Sql Server 2005 database like so: CREATE VIEW [dbo].[MeterProvingStatisticsPoint] AS SELECT CAST(0 AS BIGINT) AS \'RowNumber\', CAST(0 AS BIGINT) AS \'ProverTicketId\', CAST(0 AS INT) AS \'ReportNumber\', GETDATE() AS \'CompletedDateTime\', CAST(1.1 AS float) AS \'MeterFactor\', CAST(1.1 AS float) AS \'Density\', CAST(1.1 AS float) AS \'FlowRate\', CAST(1.1 AS float) AS \'Average\', CAST(1.1 AS

Entity Framework and SQL Server View

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For several reasons that I don't have the liberty to talk about, we are defining a view on our Sql Server 2005 database like so: CREATE VIEW [dbo].[MeterProvingStatisticsPoint] AS SELECT CAST(0 AS BIGINT) AS 'RowNumber', CAST(0 AS BIGINT) AS 'ProverTicketId', CAST(0 AS INT) AS 'ReportNumber', GETDATE() AS 'CompletedDateTime', CAST(1.1 AS float) AS 'MeterFactor', CAST(1.1 AS float) AS 'Density', CAST(1.1 AS float) AS 'FlowRate', CAST(1.1 AS float) AS 'Average', CAST(1.1 AS float) AS 'StandardDeviation', CAST(1.1 AS float) AS 'MeanPlus2XStandardDeviation', CAST(1.1 AS float) AS