Oracle date format exception: invalid number

Oracle Time format Invalid number

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Field name	type	remarks
flightDate	varchar	Format ：yyyy-mm-dd hh24:mi:ss

1. Query statement ：

    select
       TO_CHAR(xxx.flightDate,'hh24:mi')
    from 
        xxx

2. Query results ：

    SELECT
        TO_CHAR(HANDOVER_TIME,'hh24:mi') 
    FROM
        "T_DOA_FLIGHT_BIZ" 
    WHERE
        HANDOVER_TIME IS NOT NULL
    > ORA-01722:  Invalid number 
    ​
    >  Time : 0.026s

3. error analysis ：

   TO_CHAR Function official description

   TO_CHAR (datetime) converts a datetime or interval value of DATE, TIMESTAMP, TIMESTAMPWITHTIMEZONE, or TIMESTAMPWITHLOCALTIME``ZONE datatype to a value of VARCHAR2 datatype in the format specified by the date format fmt.

   TO_CHAR Function receive only receive not receive VARCHAR Data of type ！

4. terms of settlement ：

   Use TO_DATE Function will VARCHAR Type of data to DATETIME type , And then use TO_CHAR.

    select
       TO_CHAR(TO_DATE(xxx.flightDate,'yyyy-mm-dd hh24:mi:ss'),'hh24:mi')
    from 
        xxx

5. summary