I read that the data type can be used to store files. According to MySQL manual page on Blob, A BLOB is a binary large object that can hold a variable amount of data. Since it’s a data type specific to store binary data it’s common to use it to store files in binary format, … Read more
There’s a clear best option out of the three you suggested (plus one from the comments). BIGINT — uses just 8 bytes, but the largest BIGINT only has 19 decimal digits; if you divide by 1018, the largest value you can represent is 9.22, which isn’t enough range. DOUBLE — only has 15–17 decimal digits … Read more
You almost never want to join sys.columns.system_type_id = sys.types.system_type_id. This will lead to duplicate records in the case of user-defined types. There are two JOINs which do make sense. Both of them work equivalently for built-in types. sys.columns.user_type_id = sys.types.user_type_id For a built-in type, it returns the built-in type. For a user-defined type, it returns … Read more
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I think you are trying to specify database column type. You could use data annotations as described in this article. Here is an example : [Table(“People”)] public class Person { public int Id { get; set; } [Column(TypeName = “varchar”)] public string Name { get; set; } [Column(TypeName=”date”)] public DateTime DOB { get; set; } … Read more
CONVERT takes the column name, not a string containing the column name; your current expression tries to convert the string A.my_NvarcharColumn to an integer instead of the column content. SELECT convert (int, N’A.my_NvarcharColumn’) FROM A; should instead be SELECT convert (int, A.my_NvarcharColumn) FROM A; Simple SQLfiddle here.
If you want to created an “unbounded” varchar column just use varchar without a length restriction. From the manual: If character varying is used without length specifier, the type accepts strings of any size So you can use: create table foo ( unlimited varchar ); Another alternative is to use text: create table foo ( … Read more
Use the serial type for automatically incrementing unique ids. If you plan to have more than two billion entries, use bigserial. serial is the PostgresSQL equivalent of MySQL’s AUTO_INCREMENT. PostgresSQL Documentation: Numeric Types
The advantages you have for choosing a character datatype as a primary key field is that you may choose what data it can show. As an example, you could have the email address as the key field for a users table. The eliminates the need for an additional column. Another advantage is if you have … Read more
Use uuid. PostgreSQL has the native type for a reason. It stores the uuid internally as a 128-bit binary field. Your other proposed options store it as hexadecimal, which is very inefficient in comparison. Not only that, but: uuid does a simple bytewise sort for ordering. text, char and varchar consider collations and locales, which … Read more