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Preventing Duplicate INSERTs in SQL
Inserting data into a database table is crucial, but sometimes avoiding duplicate entries becomes a challenge. One such instance arises when inserting values provided by user input. In this scenario, users may mistakenly submit duplicate records, leading to data redundancy and integrity issues.
To address this problem, one effective solution is to utilize SQL's MERGE statement. The MERGE statement combines the functionality of INSERT, UPDATE, and DELETE operations into a single statement, providing fine-grained control over data manipulation. It allows you to insert new rows only if they do not already exist in the table.
For your specific table named "Delegates," with fields ID, MemberNo, FromYr, and ToYr, you can use the following MERGE statement to prevent duplicate insertions:
<code class="sql">MERGE INTO Delegates D USING (values(@MemNo, @FromYr,@ToYr)) X ([MemNo],[FromYr],[ToYr]) ON (insert unique key join) WHEN NOT MATCHED BY TARGET THEN INSERT ([MemNo],[FromYr],[ToYr])) VALUES (X.[MemNo],X.[FromYr],X.[ToYr]);</code>
In this query:
By using this MERGE statement, you can ensure that duplicate rows are not inserted into your Delegates table, preserving data integrity and preventing redundant records.
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