Value Type

GenORM categorizes SQL expressions into the following three types, and prevents SQL errors by mapping each SQL expression to a Go type.

• Literal
• Expr
• Column

Also, "the type itself implements sql.Scanner and the pointer implements driver.Valuer" such as uuid.UUID can be placed in the genorm.ExprTypeinterface.

Literal

This value is treated as a literal in SQL.

The value of the type that applies to the genorm.ExprTypeinterface is literal.

Values of primitive types such as bool, int, and float32 that cannot be placed in the genorm.ExprType interface can be converted to the genorm.WrappedPrimitive[T] type using the `genorm. It can be used as a literal.

Expr

This is a value that is handled as an expression in SQL.

This value has as its type parameter the type of the table used in constructing the expr and the type that applies to the genorm.ExprTypeinterface to which the expr corresponds.

For example, the return value of genorm.EqLit(user.IDExpr, uuid.New()) is an Expr with *orm.UserTable and bool as type parameters because it uses the id column of the users table and is a boolean in SQL.

Normal table columns can be used as Expr by using a variable named ~Expr in the package corresponding to the table, such as users.IDExpr for an id column in a users table. Columns of a joined table can be converted to Expr of the table using the function ~ParseExpr corresponding to the table. For example, if users INNER JOIN messages ON users.id = messages.user_id, you can use the id column of the users table by using orm.MessageUserParseExpr(user.ID).

Column

This value is treated as a column name in SQL.

This value has as type parameters the type corresponding to the table containing the column and the type that applies to the genorm.ExprTypeinterface to which Expr corresponds.

Normal table columns can be used as columns by using variables in the package corresponding to the table, such as users.ID for an id column in the users table. Columns of the joined table can be converted to columns of the table using the function ~Parse corresponding to the table. For example, if users INNER JOIN messages ON users.id = messages.user_id, then orm.MessageUserParse(user.ID) can be used as Column for the id column of the users table.