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POMySQL: Perform type conversion in BEFORE INSERT trigger
 

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  1. POMySQL: Perform type conversion in BEFORE INSERT trigger
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    <p>I have two tables, <code>pattern</code> and <code>pattern_optimized</code>. Some of the fields in the <code>pattern</code> table are defined as <code>BIGINT(20) DEFAULT '-1'</code>, which is way too big for the data they hold; Additionally, <code>-1</code> is used as "not set" (zero is a valid value) - no other negative values are used otherwise.</p> <p>The <code>pattern_optimized</code> table uses a new data format for these rows, defining them as <code>INT(10) UNSIGNED DEFAULT NULL</code>. I would now like to copy the data from <code>pattern</code> to the <code>pattern_optimized</code> table. </p> <p>This would be easily done using <code>INSERT INTO pattern_optimized SELECT * FROM pattern</code>, but obviously all negative values are out of range now, resulting in warnings like this:</p> <pre><code>100 row(s) affected, 64 warning(s): 1264 Out of range value for column 'version' at row 1 1264 Out of range value for column 'triggered' at row 1 ... Records: 100 Duplicates: 0 Warnings: 357 </code></pre> <p>My first idea was to create a <code>BEFORE INSERT</code> trigger as follows:</p> <pre><code>CREATE TRIGGER `negativeValueFix` BEFORE INSERT ON `pattern_optimized` FOR EACH ROW BEGIN IF new.version &lt; 0 THEN SET new.version = NULL; END IF; -- ... END </code></pre> <p>but unfortunately this doesn't help either: The same warning pops up and all values that used to be <code>-1</code> in the original table become <code>0</code> in the new table (instead of <code>NULL</code>, which is - apart from being implemented in the trigger - also the default for the row). It seems that MySQL converts the value even before the trigger.</p> <p>I know that I can solve this problem using a temporary table but I'd rather not do that. The <code>pattern</code> table is unpleasantly large and I don't want to do a stored procedure just for that.</p> <p>Is there any other way or am I missing some simple point?</p> <p><strong>EDIT</strong>: There are quite alot columns in the original table that suffer from the SIGNED problem, so I was hoping to somewhat automate that.</p>
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