toszter: Call me nutty, but why not declare any number of columns as primary key in your model, which django then uses to create a "hidden" pk_composite column that's just a hash of the three pk values in the row? When you do a lookup on a pk, you assume the ENTIRE combination...
If you're doing this through the GUI (SQL Server Management Studio) and the table designer you simply hold shift and click the grey area to the left of the column name & type. Then right-click and choose the option to make a primary key. Presto! ;)...
During analysis, each combination of columns is analyzed to determine uniqueness. To be inferred as a multiple column primary key candidate, the combination of columns must have a cardinality percentage that is equal or greater than the primary key threshold. The cardinality percentage of a combinati...
Does GreenDAO support primary key on multiple columns? I'm usingProperty's methodprimaryKey()on two columns but it doesn't work. I'm getting exception: Caused by: android.database.sqlite.SQLiteException: table "table" has more than one primary key How to create primary key on multiple colu...
本次讨论一下index(每列作为一个索引,单列索引)和Multiple-Column Indexes(多列作为一个索引,最多16列,复合索引)使用场景。 常见新建或添加索引的方式: 方式一,建表时新建 CREATETABLEtest ( idINTNOTNULL, last_nameCHAR(30)NOTNULL, first_nameCHAR(30)NOTNULL,PRIMARYKEY(id),--单列索引INDEXname (last...
I have a requirement where most of the tables have a two column relationship with others. For instance, Table 1 (related to Table 2): RoundID + EntityID => Primary Key Table 2: RoundID + EntityID => Primary Key Table 1 (also related to Table 3) also has similar relationships with ...
It's actually just a typo, you forgot a comma after the NOT NULL on the second line, before the line with the PRIMARY KEY. The server doesn't chuck an error there because you can actually say "PRIMARY KEY" directly for a single column, that's valid - so only after you started spec...
A multiple-column index can be considered a sorted array, the rows of which contain values that are created by concatenating the values of the indexed columns. Note As an alternative to a composite index, you can introduce a column that is“hashed”based on information from other columns. If...
Bug #25544Multiple column unique key allows multiple rows? Submitted:11 Jan 2007 14:25Modified:24 Feb 2014 9:37 Reporter:Andre TimmerEmail Updates: Status:Not a BugImpact on me: None Category:MySQL ServerSeverity:S2 (Serious) Version:5.0.18OS:Any ...
(just for that session) a value for sql_generate_invisible_primary_key to OFF, drop the column that is a primary key and add the primary key of your choice. Then you can revert that system variable to ON, if you wish. Your request for the change of behaviour with that system variable...