etsted Posted March 28, 2014 Share Posted March 28, 2014 (edited) how should the UNIQUE KEY syntax look? // is this right? UNIQUE KEY username (username, email)? // or this?? because i think this is the right syntax, but i have seen some use the above. Why? UNIQUE KEY(username, email)?? Is both legit? Edited March 28, 2014 by etsted Link to comment Share on other sites More sharing options...
Ingolme Posted March 28, 2014 Share Posted March 28, 2014 There's a full reference for MySQL syntax here: http://dev.mysql.com/doc/refman/5.1/en/create-table.htmlAccording to it, this syntax is valid:col_name INT UNIQUE KEY col_name column_definition column_definition:data_type [NOT NULL | NULL] [DEFAULT default_value][AUTO_INCREMENT] [UNIQUE [KEY] | [PRIMARY] KEY][COMMENT 'string'][COLUMN_FORMAT {FIXED|DYNAMIC|DEFAULT}][sTORAGE {DISK|MEMORY|DEFAULT}][reference_definition] And this syntax is valid as well:col_name INT,UNIQUE KEY index_name (col_name) col_name column_definition [CONSTRAINT [symbol]] UNIQUE [iNDEX|KEY][index_name] [index_type] (index_col_name,...)[index_option] ... The square brackets indicate that a symbol is optional. [index_name] can be omitted, resulting in this: UNIQUE KEY (col_name) Link to comment Share on other sites More sharing options...
etsted Posted March 29, 2014 Author Share Posted March 29, 2014 so the line "username" after KEY just points out where mysql should look? Link to comment Share on other sites More sharing options...
Ingolme Posted March 29, 2014 Share Posted March 29, 2014 It creates an index called "username" which also happens to be the same name as the column. Indexing is a bit complicated, I can't explain it in detail from memory but if you're interested you can look it up. An index is a column you're expecting to use to search for data in the table. Tables are optimized to search for results fastest for columns that are indexed. Link to comment Share on other sites More sharing options...
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