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POHow to create delete trigger in SQL on deletion of one record from child table updates the records count in parent table?
 

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  1. POHow to create delete trigger in SQL on deletion of one record from child table updates the records count in parent table?
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    <p>I have created two tables .First is of magzine</p> <pre><code>CREATE TABLE [dbo].[Magzine]( [ID] [int] IDENTITY(1,1) NOT NULL, [Name] [nvarchar](350) NULL, [MagzineType] [int] NOT NULL, [TotalPages] [int] NOT NULL, [DateCreated] [datetime] NOT NULL, [Active] [bit] NOT NULL, CONSTRAINT [PK_tblMagzine] PRIMARY KEY CLUSTERED ( [ID] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY] GO </code></pre> <p>which has a column name TotalPages which holds for the count of total pages in the magzine</p> <p>and here is the MagzinePage Table.</p> <pre><code>CREATE TABLE [dbo].[MagzinePage]( [ID] [int] IDENTITY(1,1) NOT NULL, [MagzineID] [int] NOT NULL, [Title] [nvarchar](255) NULL, [SubTitle] [nvarchar](255) NULL, [Photo] [nvarchar](255) NULL, [Description] [nvarchar](2000) NULL, [DateCreated] [datetime] NOT NULL, [CreatedBy] [nvarchar](25) NOT NULL, [Active] [bit] NOT NULL, [IsMapped] [bit] NULL, CONSTRAINT [PK_tblPage] PRIMARY KEY CLUSTERED ( [ID] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY] GO </code></pre> <p>I have created a trigger on the insertion of data in magzinePage table which can take care of the total number of records inserted in the table against an ID here is the Trigger</p> <pre><code>Alter TRIGGER trgAfterInsert ON [dbo].[MagzinePage] FOR INSERT AS Declare @MagzineID int; Declare @TotalPages int; Set @MagzineID= (Select Top 1 MagzineID From MagzinePage Order By ID Desc) Set @TotalPages = (Select Count(MagzineID) from MagzinePage Where MagzineID=@MagzineID Group By MagzinePage.MagzineID) Update Magzine Set TotalPages=@TotalPages Where ID= @MagzineID PRINT 'AFTER INSERT trigger fired.' GO </code></pre> <p>Now I want to create a trigger for the purpose that can help decrement the total number of pages in the Magzine table whenever a record from the magzinePage table is deleted.</p> <p>kindly do me favour to figure a way out for that. Thanks. </p>
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    1. USSoftBuilders Pk
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    1. COYour current insert trigger is broken - a single `insert` could create rows for multiple magazines, but your trigger will only update one. Also, why do you think you need to store the count? If you perform the count during data retrieval (e.g. `SELECT`), it will always be correct.
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      1. POHow to create delete trigger in SQL on deletion of one record from child table updates the records count in parent table?
      1. USDamien_The_Unbeliever
    2. CO@Damien_The_Unbelieve I believe that this trigger is working fine and I need the count because i need to show a grid having all the details about the magzine.If i go with retrieving data every time than it might take long .What you suggest?
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      1. POHow to create delete trigger in SQL on deletion of one record from child table updates the records count in parent table?
      1. USSoftBuilders Pk
    3. COI've added a section to the end of my answer showing why your trigger is broken.
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      1. POHow to create delete trigger in SQL on deletion of one record from child table updates the records count in parent table?
      1. USDamien_The_Unbeliever
 

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