How Can I Identify Gaps in MySQL Auto-Increment Sequences?

MySQL Auto-Increment Sequence Gap Detection

Database integrity issues can arise from missing values in tables with auto-increment columns. This often happens during data import or modification. This article shows how to identify these gaps using a SQL query.

Query to Locate Missing Numbers

The following query pinpoints missing values in an auto-increment sequence:

<code class="language-sql">SELECT (t1.id + 1) as gap_starts_at,
       (SELECT MIN(t3.id) -1 FROM arrc_vouchers t3 WHERE t3.id > t1.id) as gap_ends_at
FROM arrc_vouchers t1
WHERE NOT EXISTS (SELECT t2.id FROM arrc_vouchers t2 WHERE t2.id = t1.id + 1)
HAVING gap_ends_at IS NOT NULL</code>

Understanding the Query

• gap_starts_at: Indicates the beginning of a gap in the sequence.
• gap_ends_at: Shows the end of the gap.

This query effectively detects gaps by searching for consecutive missing numbers in the auto-increment sequence.

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