Should I use MyISAM or InnoDB Tables for my MySQL Database?

Question

I have the following two tables in my database (the indexing is not complete as it will be based on which engine I use):

Table 1:

CREATE TABLE `primary_images` (
  `imgId` smallint(6) unsigned NOT NULL AUTO_INCREMENT,
  `imgTitle` varchar(255) DEFAULT NULL,
  `view` varchar(45) DEFAULT NULL,
  `secondary` enum('true','false') NOT NULL DEFAULT 'false',
  `imgURL` varchar(255) DEFAULT NULL,
  `imgWidth` smallint(6) DEFAULT NULL,
  `imgHeight` smallint(6) DEFAULT NULL,
  `imgDate` datetime DEFAULT NULL,
  `imgClass` enum('jeans','t-shirts','shoes','dress_shirts') DEFAULT NULL,
  `imgFamily` enum('boss','lacoste','tr') DEFAULT NULL,
  `imgGender` enum('mens','womens') NOT NULL DEFAULT 'mens',
  PRIMARY KEY (`imgId`),
  UNIQUE KEY `imgDate` (`imgDate`)
)

Table 2:

CREATE TABLE `secondary_images` (
  `imgId` smallint(6) unsigned NOT NULL AUTO_INCREMENT,
  `primaryId` smallint(6) unsigned DEFAULT NULL,
  `view` varchar(45) DEFAULT NULL,
  `imgURL` varchar(255) DEFAULT NULL,
  `imgWidth` smallint(6) DEFAULT NULL,
  `imgHeight` smallint(6) DEFAULT NULL,
  `imgDate` datetime DEFAULT NULL,
  PRIMARY KEY (`imgId`),
  UNIQUE KEY `imgDate` (`imgDate`)
)

Table 1 will be used to create a thumbnail gallery with links to larger versions of the image. imgClass, imgFamily, and imgGender will refine the thumbnails that are shown.

Table 2 contains images related to those in Table 1. Hence the use of primaryId to relate a single image in Table 1, with one or more images in Table 2. This is where I was thinking of using the Foreign Key ability of InnoDB, but I'm also familiar with the ability of Indexes in MyISAM to do the same.

Without delving too much into the remaining fields, imgDate is used to order the results.

Last, but not least, I should mention that this database is READ ONLY. All data will be entered by me. I have been told that if a database is read only, it should be MyISAM, but I'm hoping you can shed some light on what you would do in my situation.

Answer 1

Always use InnoDB by default.

In MySQL 5.1 later, you should use InnoDB. In MySQL 5.1, you should enable the InnoDB plugin. In MySQL 5.5, the InnoDB plugin is enabled by default so just use it.

The advice years ago was that MyISAM was faster in many scenarios. But that is no longer true if you use a current version of MySQL.

There may be some exotic corner cases where MyISAM performs marginally better for certain workloads (e.g. table-scans, or high-volume INSERT-only work), but the default choice should be InnoDB unless you can prove you have a case that MyISAM does better.

Advantages of InnoDB besides the support for transactions and foreign keys that is usually mentioned include:

• InnoDB is more resistant to table corruption than MyISAM.
• Row-level locking. In MyISAM, readers block writers and vice-versa.
• Support for large buffer pool for both data and indexes. MyISAM key buffer is only for indexes.
• MyISAM is stagnant; all future development will be in InnoDB.

See also my answer to MyISAM versus InnoDB

Answer 2

MyISAM won't enable you to do mysql level check. For instance if you want to update the imgId on both tables as a single transaction:

START TRANSACTION;
UPDATE primary_images SET imgId=2 WHERE imgId=1;
UPDATE secondary_images SET imgId=2 WHERE imgId=1;
COMMIT;

Another drawback is integrity check, using InnoDB you can do some error check like to avoid duplicated values in the field UNIQUE KEY imgDate (imgDate). Trust me, this really come at hand and is way less error prone. In my opinion MyISAM is for playing around while some more serious work should rely on InnoDB.

Hope it helps