Incorrect parameter count in the call to native function 'ISNULL'

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Incorrect parameter count in the call to native function 'ISNULL'
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
	at com.mysql.jdbc.Util.getInstance(Util.java:386)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1053)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4074)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4006)
	at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2468)
	at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2629)
	at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2713)
	at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1794)
	at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1712)
	at org.apache.commons.dbcp.DelegatingStatement.executeUpdate(DelegatingStatement.java:225)

1 queries executed, 0 success, 1 errors, 0 warnings

 ：select count(isnull(depart_teacher,'')) from t_depart_info LIMIT 0, 1000

 ： 1582
Incorrect parameter count in the call to native function 'isnull'

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