使用MERGE语句将记录更新/插入到表中

Question

I did this 3 years ago with DB2 but can't remember how.

All I want to do is Update/Insert a record into a table. Rather than test for its existence and changing my DML, I want to do this with a parameterized insert/update(merge) T-SQL statement. I believe the procedure compiler optimizer will make this the most efficient method.

USE [MY_DB]
GO

/****** Object:  Table [dbo].[map_locations]    Script Date: 10/11/2015 9:29:26 PM ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

CREATE TABLE [dbo].[map_locations](
    [loc_min_lat] [varchar](5) NOT NULL,
    [loc_min_lng] [varchar](6) NOT NULL,
    [loc_id] [int] NULL,
    [center] [varchar](20) NOT NULL CONSTRAINT [DF__map_locs__call___5E4ADDA8]  DEFAULT (''),
 CONSTRAINT [PK__map_map_locs__79C80F94] PRIMARY KEY CLUSTERED 
(
    [map_locations_lat] ASC,
    [map_locations_lng] ASC,
    [center] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO

Simply put, I want to be able to insert a record into the above table if it does not violate the PK but update it if the record (from a PK perspective) exists.

I have been researching and all the MS SQL examples are for two table merges. I am passing in a record via parameters.

I am working in Delphi XE10 (not that that should matter) and the database is MS SQL 2012.

Any help appreciate.

Answer 1

When you say "rather than", I assume you're using Sql Server 2008 or later and are wanting to use its Merge command (apologies for the earlier version of this answer).

Here's a sample TransactSql script (tested and working, but using my table structure) which assumes you know the PK in advance:

declare @id int

select @id = 1

merge table1 as dest
using (values (@id, 'name1'))
    as source (id, name)
    on dest.id = @id
when matched then
    update 
    set name = source.name
when not matched then
    insert ( id, name)
    values ( source.id, source.name);

select * from table1

From a Delphi app, you'd want to write that as a parameterized query, or, better, a parameterized call to a stored proc on the server.

These days, no Delphi-tagged q about Sql seems complete without a mention of Sql-Injection, but using a parameterized query should minimise the risk of that.