Database Layer

make() builds model instances from the factory's definition() without saving them; create() builds them the same way and then persists each one with save(). Both return a single model, or an Eloquent Collection once count() is set.

A seeder is a class in database/seeders with a run() method; DatabaseSeeder is the root and runs others through $this->call(). php artisan db:seed runs DatabaseSeeder, --class runs one seeder, and migrate --seed seeds after migrating.

It writes a timestamped file in database/migrations that returns an anonymous class extending Migration, with up() creating the listings table and down() dropping it. migrate runs pending up() methods as one batch; migrate:rollback runs down() for the last batch.

paginate() runs a COUNT query plus a LIMIT/OFFSET query and returns a LengthAwarePaginator with totals and page numbers; simplePaginate() runs one LIMIT/OFFSET query for next/previous only; cursorPaginate() filters on the ordered columns instead of using an offset.

get() returns an Illuminate\Support\Collection of stdClass rows, empty when nothing matches; first() returns one stdClass or null; value('total') returns that column from the first row or null. Only firstOrFail() and sole() throw.

DB::transaction() begins, runs the closure, commits on success, and on any exception rolls back and rethrows, returning the closure's value. The manual trio leaves every path to you, so a missed rollBack() leaves the transaction open on the connection.

It adds an unsigned big-integer seller_id column and a foreign key to sellers.id that deletes listings when their seller is deleted. constrained() returns the foreign-key definition, so a nullable() chained after it never reaches the column.

The chain compiles to shop_id = 3 and status = 'paid' or status = 'refunded'; SQL evaluates and before or, so every refunded order from any shop matches. Group the alternatives in a closure passed to where(), or use whereIn().

Returning a paginator serialises it with the records under data plus metadata. paginate() adds total, last_page, last_page_url and a links array; simplePaginate() has page URLs but no total; cursorPaginate() has next_cursor, prev_cursor and their URLs instead of page numbers.

DB::listen() registers a closure that receives a QueryExecuted event after every query, with sql, bindings, time in milliseconds and connectionName. whenQueryingForLongerThan() instead fires once when a connection's total query time exceeds a threshold.

for() gives created models a belongsTo parent, from a factory or an existing model; has() creates hasMany or belongsToMany children after the parent is saved; hasAttached() attaches belongsToMany models with pivot values. hasAppointments(3) is has() driven by the appointments() relation.

A state is an attribute override layered on top of definition(); a named state is a factory method that returns $this->state(...). sequence() adds a state that cycles through its values one record at a time.

rollback runs down() for the latest batch; reset runs down() for every migration; refresh does reset (or a --step rollback) and migrates again; fresh drops every table with db:wipe and migrates, never calling down().

A paginator builds its links from the current URL without its query string and adds only the page parameter, so ?sport=trail is lost. withQueryString() copies the whole current query string, appends() adds chosen keys, and fragment() adds a #hash.

Start from shops, leftJoin orders with the month and status conditions inside the join closure, selectRaw a coalesced sum, and groupBy the shop columns. A date filter in where() would drop zero-sale shops, and calling sum() returns one number.

when($value, $callback) runs the callback only if $value is truthy, passing the builder and the value. The string "0" is falsy in PHP, so a shop_id of 0 skips the filter and returns every shop's rows.

It runs right after the outermost transaction commits, or immediately if no transaction is open. If the transaction, or the savepoint it was registered in, rolls back, the callback is discarded and never runs.

Selects use a read host and writes use the write host. Without sticky, a read after a write in the same request can hit a lagging replica and miss the new points; reads inside a transaction always use the writer.

Only concurrency errors are retried: SQLSTATE 40001, deadlock and lock-wait-timeout messages, or SQLite's 'database is locked'. Any other exception is rolled back and rethrown at once. A retry re-runs the whole closure, so non-database side effects inside it happen again.

The skeleton lists fakerphp/faker under require-dev, so a --no-dev production install lacks it and fake() fails; and db:seed asks for confirmation in production, cancelling non-interactive runs without --force. Seed production from a dedicated seeder with fixed values.

definition() runs once per appointment, and a nested Doctor::factory() is created each time to supply the key. Create a pool first and chain recycle($doctors), so the factory picks a random existing doctor instead.

Existing rows need a value: add it with a default, or add it nullable, backfill, then make it required with change(). change() redefines the whole column, so any modifier not restated, such as default or comment, is dropped.

The cursor stores the last row's created_at and the next page asks for rows strictly older, so rows sharing that timestamp are skipped. Order by a unique combination, such as created_at then id, with non-null columns from the paginated table.

lockForUpdate() only appends FOR UPDATE; without DB::transaction() around the read and the write the lock ends with the statement. On SQLite, the skeleton default, the grammar emits no lock clause at all.

Values passed to where(), whereIn(), insert() and update() are bound as PDO parameters. Column and table names are only quoted, and DB::raw() or selectRaw/whereRaw/orderByRaw strings are pasted verbatim, so user input there must go through their ? bindings or an allowlist.

migrate --pretend prints the SQL pending migrations would run without executing it; queries a migration reads return empty. schema:dump writes the schema, with migrations rows, to database/schema/<connection>-schema.sql, and --prune deletes database/migrations.

links() renders the Tailwind pagination view by default. Pass a view name to links(), set a default with Paginator::defaultView() or useBootstrapFive(), publish the views to edit them, and use onEachSide() to change how many page links surround the current page.