flink sql添加 null值 字段

hi、 我现在使用flink sql完成如下sql语句，但是程序无法运行，请问这个功能要怎么实现： select null as person_uuid from tablename 抛出异常： org.apache.flink.client.program.ProgramInvocationException: The main method caused an error: SQL validation failed. From line 1, column 47 to line 1, column 50: Illegal use of 'NULL' at org.apache.flink.client.program.PackagedProgram.callMainMethod(PackagedProgram.java:302) at org.apache.flink.client.program.PackagedProgram.invokeInteractiveModeForExecution(PackagedProgram.java:198) at org.apache.flink.client.ClientUtils.executeProgram(ClientUtils.java:149) at org.apache.flink.client.cli.CliFrontend.executeProgram(CliFrontend.java:699) at org.apache.flink.client.cli.CliFrontend.run(CliFrontend.java:232) at org.apache.flink.client.cli.CliFrontend.parseParameters(CliFrontend.java:916) at org.apache.flink.client.cli.CliFrontend.lambda$main$10(CliFrontend.java:992) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:422) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1917) at org.apache.flink.runtime.security.contexts.HadoopSecurityContext.runSecured(HadoopSecurityContext.java:41) at org.apache.flink.client.cli.CliFrontend.main(CliFrontend.java:992) Caused by: org.apache.flink.table.api.ValidationException: SQL validation failed. From line 1, column 47 to line 1, column 50: Illegal use of 'NULL' at org.apache.flink.table.planner.calcite.FlinkPlannerImpl.org $apache$flink$table$planner$calcite$FlinkPlannerImpl$$validate(FlinkPlannerImpl.scala:146) at org.apache.flink.table.planner.calcite.FlinkPlannerImpl.validate(FlinkPlannerImpl.scala:108) at org.apache.flink.table.planner.operations.SqlToOperationConverter.convert(SqlToOperationConverter.java:187) at org.apache.flink.table.planner.delegation.ParserImpl.parse(ParserImpl.java:78) at org.apache.flink.table.api.internal.TableEnvironmentImpl.sqlQuery(TableEnvironmentImpl.java:664) at com.akulaku.blade.main.StreamingMain.main(StreamingMain.java:103) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.apache.flink.client.program.PackagedProgram.callMainMethod(PackagedProgram.java:288) ... 11 more Caused by: org.apache.calcite.runtime.CalciteContextException: From line 1, column 47 to line 1, column 50: Illegal use of 'NULL' at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at org.apache.calcite.runtime.Resources$ExInstWithCause.ex(Resources.java:457) at org.apache.calcite.sql.SqlUtil.newContextException(SqlUtil.java:839) at org.apache.calcite.sql.SqlUtil.newContextException(SqlUtil.java:824) at org.apache.calcite.sql.validate.SqlValidatorImpl.newValidationError(SqlValidatorImpl.java:5089) at org.apache.calcite.sql.validate.SqlValidatorImpl.inferUnknownTypes(SqlValidatorImpl.java:1906) at org.apache.calcite.sql.validate.SqlValidatorImpl.inferUnknownTypes(SqlValidatorImpl.java:1968) at org.apache.calcite.sql.validate.SqlValidatorImpl.expandSelectItem(SqlValidatorImpl.java:479) at org.apache.calcite.sql.validate.SqlValidatorImpl.validateSelectList(SqlValidatorImpl.java:4255) at org.apache.calcite.sql.validate.SqlValidatorImpl.validateSelect(SqlValidatorImpl.java:3523) at org.apache.calcite.sql.validate.SelectNamespace.validateImpl(SelectNamespace.java:60) at org.apache.calcite.sql.validate.AbstractNamespace.validate(AbstractNamespace.java:84) at org.apache.calcite.sql.validate.SqlValidatorImpl.validateNamespace(SqlValidatorImpl.java:1110) at org.apache.calcite.sql.validate.SqlValidatorImpl.validateQuery(SqlValidatorImpl.java:1084) at org.apache.calcite.sql.SqlSelect.validate(SqlSelect.java:232) at org.apache.calcite.sql.validate.SqlValidatorImpl.validateScopedExpression(SqlValidatorImpl.java:1059) at org.apache.calcite.sql.validate.SqlValidatorImpl.validate(SqlValidatorImpl.java:766) at org.apache.flink.table.planner.calcite.FlinkPlannerImpl.org $apache$flink$table$planner$calcite$FlinkPlannerImpl$$validate(FlinkPlannerImpl.scala:141) ... 21 more Caused by: org.apache.calcite.sql.validate.SqlValidatorException: Illegal use of 'NULL' at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at org.apache.calcite.runtime.Resources$ExInstWithCause.ex(Resources.java:457) at org.apache.calcite.runtime.Resources$ExInst.ex(Resources.java:550)*来自志愿者整理的flink邮件归档