带有复合索引的mysql唯一索引

Question

I have one table in mysql as follows :

CREATE TABLE `demo_tbl` (
    `id`        MEDIUMINT(8) NOT NULL,
    `uniquefld` VARCHAR(20) NULL,
    `field1`    VARCHAR(20) NULL,
    PRIMARY KEY (`id`),
    UNIQUE INDEX `ux_uniquefld` (`uniquefld` ASC),
    INDEX `ix_uniquefld_field1` (`uniquefld` ASC, `field1` ASC)
);

Here I have created 2 indexes, one unique index for uniquefld field and another is for 2 fields uniquefld & field1 .

Is there any way to create single index instead of two with uniqueness for uniquefld ?

Answer 1

why do you need to index ix_uniquefld_field1? since uniquefld is unique, any query on uniquefld+field1 can do just fine by accessing the index on ux_uniquefld.

Answer 2

CREATE TABLE demo_tbl (
    id MEDIUMINT NOT NULL PRIMARY KEY,
    uniquefld VARCHAR(20) CONSTRAINT uid_uniquefld UNIQUE,
    field1    VARCHAR(20),
);
CREATE INDEX idx_field1 ON demo_tbl (field1);

This will Work much effectively.