SERIAL CONSISTENCY 

Sets consistency for lightweight transactions (LWT).

Sets consistency for lightweight transaction. LWT use IF EXISTS and IF NOT EXISTS. Valid values are: SERIAL and LOCAL_SERIAL.

Tip: To set the consistency level of non-lightweight transaction, see CONSISTENCY.

Synopsis 

SERIAL CONSISTENCY [level]
Legend
Syntax conventions Description
UPPERCASE Literal keyword.
Lowercase Not literal.
Italics Variable value. Replace with a user-defined value.
[] Optional. Square brackets ( [] ) surround optional command arguments. Do not type the square brackets.
( ) Group. Parentheses ( ( ) ) identify a group to choose from. Do not type the parentheses.
| Or. A vertical bar ( | ) separates alternative elements. Type any one of the elements. Do not type the vertical bar.
... Repeatable. An ellipsis ( ... ) indicates that you can repeat the syntax element as often as required.
'Literal string' Single quotation ( ' ) marks must surround literal strings in CQL statements. Use single quotation marks to preserve upper case.
{ key : value } Map collection. Braces ( { } ) enclose map collections or key value pairs. A colon separates the key and the value.
<datatype1,datatype2> Set, list, map, or tuple. Angle brackets ( < > ) enclose data types in a set, list, map, or tuple. Separate the data types with a comma.
cql_statement; End CQL statement. A semicolon ( ; ) terminates all CQL statements.
[--] Separate the command line options from the command arguments with two hyphens ( -- ). This syntax is useful when arguments might be mistaken for command line options.
' <schema> ... </schema> ' Search CQL only: Single quotation marks ( ' ) surround an entire XML schema declaration.
@xml_entity='xml_entity_type' Search CQL only: Identify the entity and literal value to overwrite the XML element in the schema and solrConfig files.

Examples 

Display current SERIAL CONSISTENCY status.

SERIAL CONSISTENCY
Reports the current setting.
Current serial consistency level set to SERIAL.
Set the serial consistency level with a value.
SERIAL CONSISTENCY LOCAL_SERIAL
Confirms the level is set.
Serial consistency level set to LOCAL_SERIAL.
Note: Trace transactions to compare the difference between INSERT statements with and without IF EXISTS.

Write data using IF NOT EXISTS.

INSERT INTO cycling.cyclist_name (id, firstname , lastname ) 
   VALUES (e7ae5cf3-d358-4d99-b900-85902fda9bb0,'Alex','FRAME' ) 
   IF NOT EXISTS ;

Since the record already exists, the insert is not applied.

[applied] | id                                   | firstname | lastname
-----------+--------------------------------------+-----------+----------
     False | e7ae5cf3-d358-4d99-b900-85902fda9bb0 |      Alex |    FRAME