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Rules

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This article is generated by AI translation.

You can invoke rules in SQL with @{...}. Rules significantly reduce the effort and complexity of assembling dynamic command.

Rule syntax
@{<ruleName> [, <enableCondition OGNL> [, ruleContent ]])
info

Rules cannot be nested.

Guide​

dbVisitor ships many useful rules, grouped by purpose:

  • Argument rules: define or process data, e.g., MD5 hashing, UUID generation, encryption/decryption.
  • Result rules: process data in result sets, e.g., encryption/decryption, replace, mask.
  • Dynamic_rules: simple dynamic command, e.g., only include a param when not null.
  • Macro rules: alter the final command sent to the DB, e.g., argument-driven ordering, computed sharded table names.
  • Assist rules: no direct query/result effect; used in specific scenarios such as stored procedure helpers.

Basics​

Some rules are invoked by name, for example:

Generate a 32-character UUID as an argument
update users set str_id = @{uuid32} where id = :id

When a rule should apply only under a condition:

Append name = :name only when queryType is NAME
select * from users where status = 1 @{ifand, queryType == 'NAME', name = :name}

To ignore the enable condition and apply it directly:

Option 1: leave the condition empty
select * from users where status = 1 @{ifand, , name = :name}
Option 2: set the condition to true
select * from users where status = 1 @{ifand, true, name = :name}