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ClickHouse can run arbitrary SQL queries from the server configuration during startup. This can be useful for migrations or automatic schema creation. 
<clickhouse>
    <startup_scripts>
        <throw_on_error>false</throw_on_error>
        <scripts>
            <query>CREATE ROLE OR REPLACE test_role</query>
        </scripts>
        <scripts>
            <query>CREATE TABLE TestTable (id UInt64) ENGINE=TinyLog</query>
            <condition>SELECT 1;</condition>
        </scripts>
        <scripts>
            <query>CREATE DICTIONARY test_dict (...) SOURCE(CLICKHOUSE(...))</query>
            <user>default</user>
        </scripts>
    </startup_scripts>
</clickhouse>
ClickHouse executes all queries from the startup_scripts sequentially in the specified order. If any of the queries fail, the execution of the following queries won’t be interrupted. However, if throw_on_error is set to true, the server will not start if an error occurs during script execution. You can specify a conditional query in the config. In that case, the corresponding query executes only when the condition query returns the value 1 or true.
If the condition query returns any other value than 1 or true, the result will be interpreted as false, and the corresponding won’t be executed.