flink sql if ????????????

[kcz]

flink-1.10.1 blink_planner
if???????????????????????????????? 
Cannot apply 'IF' to arguments of type 'IF(<BOOLEAN&gt;, <TIMESTAMP(0)&gt;, 
<VARCHAR(2147483647)&gt;)'. Supported form(s): 'IF(<ANY_TYPE&gt;, 
<NUMERIC_TYPE&gt;, <NUMERIC_TYPE&gt;)'
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