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To check if a column is NULL (or not NULL ), use the special syntax of IS NULL (or IS NOT NULL ) instead of using = . Applying that to your statement, SELECT * FROM table WHERE timestamp IS NULL; should work.
Oracle reads empty strings as NULLs, while PostgreSQL treats them as empty. Concatenating NULL values with non-NULL characters results in that character in Oracle, but NULL in PostgreSQL. Oracle and PostgreSQL behave similarly in many cases, but one way they differ is in their treatment of NULLs and empty strings.
By casting "TimeStamp" to date you throw away the time part of the timestamp, so all values within one day will be considered equal and are returned in random order. It is by accident that the first rows appear in the order you desire. Don't cast to date in the ORDER BY clause if the time part is relevant for sorting.
The timestamp datatype allows you to store both date and time. However, it does not have any time zone data. It means that when you change the timezone of your database server, the timestamp value stored in the database will not change automatically.
Try timestamp is null as i use this syntax in MySQL
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