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SQL programmingYou can use the HCL OneDB™ implementation of the SQL language to develop applications for HCL OneDB™ database servers.
Guide to SQL: SyntaxThe HCL OneDB™ Guide to SQL: Syntax describes the syntax of the statements, data types, expressions, operators, and built-in functions of the HCL OneDB™ dialect of the SQL language.
SQL statementsThis chapter describes the syntax and semantics of SQL statements that are recognized by HCL OneDB™.
CREATE INDEX statementUse the CREATE INDEX statement to create an index for one or more columns in a table, or on values returned by a UDR that uses column values as arguments.
Index modesUse the index mode options of the CREATE INDEX statement to specify the behavior of the index during INSERT, DELETE, MERGE, and UPDATE operations.
Specifying Modes for Unique Indexes
Adding a Unique Index When Duplicate Values Exist in the Column

Adding a Unique Index When Duplicate Values Exist in the Column

If you attempt to add a unique index in the enabled mode but receive an error message because duplicate values are in the indexed column, take the following steps to add the index successfully:

Add the index in the disabled mode. Issue the CREATE INDEX statement again, but this time specify the DISABLED keyword.
Start a violations and diagnostics table for the target table with the START VIOLATIONS TABLE statement.
Issue a SET Database Object Mode statement to change the mode of the index to enabled. When you issue this statement, existing rows in the target table that violate the unique-index requirement are duplicated in the violations table. You receive an integrity-violation error message, however, and the index remains disabled.
Issue a SELECT statement on the violations table to retrieve the nonconforming rows that are duplicated from the target table. You might need to join the violations and diagnostics tables to get all the necessary information.
Take corrective action on the rows in the target table that violate the unique-index requirement.
After you fix all the nonconforming rows in the target table, issue the SET Database Object Mode statement again to switch the disabled index to the enabled mode. This time the index is enabled, and no integrity violation error message is returned because all rows in the target table now satisfy the new unique-index requirement.