Consider the situation where the owned entity type can also be owned by another parent entity type. Do you put foreign key references in the owned table to both parent tables? What if you have three parent types? It just doesn’t scale to large designs. A join-table decouples the join, so that the owned table … Read more
create_user INT UNSIGNED ZEROFILL cannot reference id INT, because these count as different data types for purposes of foreign key reference. Make them the same data type. The only data type difference that is permitted between columns in a foreign key relationship is length of a varchar. For example, VARCHAR(10) can reference VARCHAR(20) or vice-versa. … Read more
Finally figured this out from this post. The PRAGMA foreign_key setting does not persist but you can set it every time the connection is made in the ConnectionString. This allows you to use Visual Studio’s table adapters. Make sure you have the latest version (1.0.73.0) of system.data.sqlite installed (1.0.66.0 will not work). Change your ConnectionString … Read more
PostgreSQL automatically creates indexes on primary keys and unique constraints, but not on the referencing side of foreign key relationships. When Pg creates an implicit index it will emit a NOTICE-level message that you can see in psql and/or the system logs, so you can see when it happens. Automatically created indexes are visible in … Read more
When you add FK, you are linking a column as a child from the table you are creating, to its parent from the parent table. Hence, you need to provide the child column name, as well as the parent column name. The general syntax is CREATE TABLE table_name ( column1 datatype null/not null, column2 datatype … Read more
I personally stick with Database first when using EF on any schema that is this level of complexity. I have had issues with complex schemas in regards to code first. Maybe the newer versions are a little better, but worrying how to try and code complex relationships seems less straight forward then allowing the engine … Read more
I’m not familiar with SQLite but a little Google’ing turned up this. The documentation says If the database schema contains foreign key errors that require looking at more than one table definition to identify, then those errors are not detected when the tables are created. Instead, such errors prevent the application from preparing SQL statements … Read more
AFAIK, dropping the constraint, then rename, then add the constraint back is the only way. Backup first!
You can solve this by allowing NULL in the foreign key column tblImageFlags.resolutionTypeID. PS Bonus points to whomever tells me whether, in the case of databases, it’s “indexes” or “indices”. The plural of index should be indexes. According to “Modern American Usage” by Bryan A. Garner: For ordinary purposes, indexes is the preferable plural, not … Read more
I am supposing that you are talking about using the REFERENCES where the FOREIGN KEY keyword is not used when constraining a column inline, which is called a column-level foreign key constraint, eg. author_id INTEGER REFERENCES author(id) … instead of the table-level foreign key constraint, which is placed after the column declarations … author_id INTEGER, … Read more