The match attribute of the sqlerrmsg tag defines a string to match against the error message. In the initial implementation, this simply checks if the match string is a (case sensitive) substring of the error string returned from the database. Regex support may be implemented in the future.
All available sqlerrmsgs will be checked in order until a match is found. The first match will prevent any others being found, so make the match as exact as possible.
You may also use this as a feature to attach a default error message (perhaps more useful once type is implemented) by having an empty match string in your last error message; this will then catch all errors.
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This is the title to show if a UI message box is displayed for the custom error message. If it is not provided, a default message will be used.
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This is currently unused, but left in place for future implementation. This will be used to specify the type of error, e.g. not null, failed constraint etc.