I try to alter table to add a composite primary key with "if not exists clause" to a table. One of these column is already in a composite unique index with an other column.
I get warning code 1061 "Multiple primary key defined".
But without "IF NOT EXISTS", it works fine.
This is my example :
CREATE TABLE `HORIZON` (
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`ID` BIGINT(20) NOT NULL,
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`RANK` MEDIUMINT(4) NOT NULL,
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`CHECK_POINT` BIGINT(20) NOT NULL,
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UNIQUE INDEX `HORIZON_UIDX01` (`ID`, `RANK`)
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) COLLATE='utf8_general_ci' ENGINE=InnoDB ;
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ALTER TABLE `HORIZON` ADD PRIMARY KEY IF NOT EXISTS (`ID`, `CHECK_POINT`); /* warning code 1061 */
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ALTER TABLE `HORIZON` ADD PRIMARY KEY (`ID`, `CHECK_POINT`); /* works fine */
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