Documenting the difference between createSelectSchema & createInsertSchema

[johnrizzo4]

It was not clear to me in the doc the difference between createSelectSchema & createInsertSchema.
I propose the enhance the readme.md with the following. I'm grateful for this framework, this is my humble contribution:

createSelectSchema vs createInsertSchema

By default, Drizzle fields are optional, unless specified .notNull().

    const testTable = pgTable('test', {
        id: text('id').primaryKey(),
        optionalField: text('optionalField'),
        requiredField: text('requiredField').notNull(),
    });

createInsertSchema keep these nullable fields for the DB, optional for Zod.

    const zodTestInsertSchema = createInsertSchema(testTable);
    type TestInsertDTO = z.infer<typeof zodTestInsertSchema>;

    const data: TestInsertDTO = {
        id: "1",
        requiredField: "mandatory",
    }
    const resultInsert = zodTestInsertSchema.safeParse(data);
    console.log("Insert zod validation: ", resultInsert);   // resultInsert.success == true

On the contrary, the same code with createSelectSchema does not compile:

    const zodTestSelectSchema = createSelectSchema(testTable);
    type TestSelectDTO = z.infer<typeof zodTestSelectSchema>;

    // DOES NOT COMPILE: Property 'optionalField' is missing in type '{ id: string; requiredField: string; }' but required in type '{ id: string; optionalField: string | null; requiredField: string; }'
    const data: TestSelectDTO = {  
        id: "1",
        requiredField: "mandatory",
    }
    const resultSelect = zodTestSelectSchema.safeParse(data);
    console.log("Select zod validation: ", resultSelect);  // resultInsert.success == false

And if we remove the ": TestSelectDTO" from the code above, the compiler will not complain but at runtime the zod validation fails (.success == false).

primary keys

Drizzle makes fields nullable by default, except primary keys unless they are DB generated. In the following example, we have a regular primary key which is mandatory for Drizzle => mandatory for Zod with both createSelectSchema and createInsertSchema:

    const testTable = pgTable('test', {
        id: text('id').primaryKey(),
        optionalField: text('optionalField'),
        requiredField: text('requiredField').notNull(),
    });

    const zodTestInsertSchema = createInsertSchema(testTable);
    type TestInsertDTO = z.infer<typeof zodTestInsertSchema>;

    // DOES NOT COMPILE: Property 'id' is missing in type '{ requiredField: string; }' but required in type '{ id: string; requiredField: string; optionalField?: string | null | undefined; }'.
    const data: TestInsertDTO = {  
        requiredField: "mandatory",
    }

Changing the primary key to serial, will make the id optional for both the DB inserts and the Zod schemas generated by createInsertSchema:

    const testTable = pgTable('test', {
        id: serial('id').primaryKey(),
        optionalField: text('optionalField'),
        requiredField: text('requiredField').notNull(),
    });

    const zodTestInsertSchema = createInsertSchema(testTable);
    type TestInsertDTO = z.infer<typeof zodTestInsertSchema>;

    const data: TestInsertDTO = {    // OK.
        requiredField: "mandatory",
    }

[NickWoodward]

This ^
The docs completely gloss over this too as far as I can see?