The UUID (universally unique id) comparator type is used to avoid collisions in column names. Alternatively, you can use the timeuuid.
Timeuuid types can be entered as integers for CQL input. A value of the timeuuid type is a Type 1UUID. A Version 1 UUID includes the time of its generation and are sorted by timestamp, making them ideal for use in applications requiring conflict-free timestamps. For example, you can use this type to identify a column (such as a blog entry) by its timestamp and allow multiple clients to write to the same partition key simultaneously. Collisions that would potentially overwrite data that was not intended to be overwritten cannot occur.
A valid timeuuid conforms to the timeuuid format shown in valid literals.
Valid literal consist of these kinds of values:
blob hexadecimal defined as 0[xX](hex)+
boolean true or false, case-insensitive, not enclosed in quotation marks
numeric constant A numeric constant can consist of integers 0-9 and a minus sign prefix. A numeric constant can also be float. A float can be a series of one or more decimal digits, followed by a period, ., and one or more decimal digits. There is no optional + sign. The forms .42 and 42 are unacceptable. You can use leading or trailing zeros before and after decimal points. For example, 0.42 and 42.0. A float constant,expressed in E notation, consists of the characters in this regular expression:
'-'
?[0-9]+(
'.'
[0-9]*)?([eE][+-]?[0-9+])?
NaN and Infinity are floats.
identifier Names of tables, columns, types, and other objects are identifiers. Since keyspace and table names are used in system file names, they must start with a letter or number and can only contain alphanumeric characters and underscores. All other identifiers, such as column and user-defined function names can contain any character. To specify an identifier that contains a special character enclose the name in quotes.
integer An optional minus sign, -, followed by one or more digits.
string literal Characters enclosed in single quotation marks. To use a single quotation mark itself in a string literal, escape it using a single quotation mark. For example, use ''to make dog possessive: dog''s.
uuid 32 hex digits, 0-9 or a-f, which are case-insensitive, separated by dashes, -, after the 8th, 12th, 16th, and 20th digits. For example: 01234567-0123-0123-0123-0123456789ab
timeuuid Uses the time in 100 nanosecond intervals since 00:00:00.00 UTC (60 bits), a clock sequence number for prevention of duplicates (14 bits), plus the IEEE 801 MAC address (48 bits) to generate a unique identifier. For example: d2177dd0-eaa2-11de-a572-001b779c76e3
whitespace Separates terms and used inside string literals, but otherwise CQL ignores whitespace.