Error map
Mysql2::Error: Unknown column in field list Rails: ActiveRecord::StatementInvalid: Mysql2::Error: Unknown column 'users.nickname' in 'field list'
Ruby / Rails · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (7). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (7)
Rails: ActiveRecord::PendingMigrationError — Migrations are pending. To resolve this issue, run: bin/rails db:migrate
The database schema is behind the migration files in the app.
Laravel: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'status' in 'field list'
The SQL refers to a column that doesn't exist in the table — a missing migration, typo or wrong table.
Rails: ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR: relation "users" does not exist
Rails queried a table that isn't in the connected PostgreSQL database.
Rails: ActiveRecord::ConnectionNotEstablished: No connection pool for 'ActiveRecord::Base' found
ActiveRecord has no database connection configured or established for this process.
Rails: PG::ConnectionBad: could not connect to server: Connection refused. Is the server running on host "localhost" (127.0.0.1) and accepting TCP/IP connections on port 5432?
Rails can't reach PostgreSQL — the server is down, wrong host/port/socket, or credentials/pg_hba block it.
Rails: ActiveRecord::Deadlocked: PG::TRDeadlockDetected: ERROR: deadlock detected
Two transactions locked rows in opposite orders, so PostgreSQL aborted one.
Rails: ActiveRecord::AssociationTypeMismatch: User(#1234) expected, got "42" which is an instance of String(#5678)
You assigned the wrong kind of object (or an id string) to an association.
Two steps away (21)
MySQL ERROR 1146 (42S02): Table 'db.table' doesn't exist
The query references a table that MySQL can’t find in that database.
PostgreSQL: ERROR: relation "x" does not exist
The table/view isn’t found — missing migration, wrong schema, or a case-sensitive quoted name.
MySQL ERROR 1022 (23000): Can't write; duplicate key in table
An ALTER/CREATE produced a duplicate key or constraint name — often a foreign key name that already exists in the database.
Laravel: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'db.sessions' doesn't exist
Laravel queried a table that hasn’t been created — usually sessions, cache, jobs or a new model’s table.
WordPress: One or more database tables are unavailable. The database may need to be repaired.
WordPress can’t read one or more of its tables — they’re crashed (MyISAM), missing, or the table prefix in wp-config.php is wrong.
Laravel: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'x@example.com' for key 'users_email_unique'
The query violated a database constraint — a duplicate value in a unique column or a missing/blocked foreign key.
Rails: ActiveRecord::StatementInvalid: PG::DuplicateColumn: ERROR: column "status" of relation "orders" already exists
A migration tried to add a column/table/index that already exists.
Rails: ActiveRecord::IrreversibleMigration — This migration uses remove_column without a type; db:rollback can't reverse it
`rails db:rollback` can't undo the migration because it contains an operation Rails can't invert.
Rails: ActiveRecord::ReadOnlyRecord: Order is marked as readonly
You tried to save a record that was loaded as read-only (e.g. via `joins` in old Rails or `readonly` scope).
Rails: ActionController::InvalidAuthenticityToken (Can't verify CSRF token authenticity)
A non-GET request arrived without a valid CSRF token for the session.
Redis: Error: connect ECONNREFUSED 127.0.0.1:6379 / Could not connect to Redis at 127.0.0.1:6379: Connection refused
Nothing is listening on the Redis host/port your client uses.
Redis: Error: write EPROTO ... SSL routines:ssl3_get_record:wrong version number / Connection reset by peer (TLS vs plaintext)
The client and server disagree about TLS — plaintext client to a TLS port, or TLS client to a plaintext port.
Rails: ActiveRecord::RecordNotFound: Couldn't find User with 'id'=42
`find`/`find_by!` didn't find a row, so Rails raises (and renders a 404 in production).
Rails: ActiveRecord::RecordInvalid: Validation failed: Email can't be blank, Name is too short
`save!`/`create!`/`update!` raised because validations failed.
Rails: ActiveRecord::RecordNotUnique: PG::UniqueViolation: ERROR: duplicate key value violates unique constraint "index_users_on_email"
A unique index rejected an insert/update because the value already exists.
Ruby: NameError: uninitialized constant UsersController::User (Did you mean? Users)
Ruby (or Rails autoloading) couldn't find a class or module with that name in the current scope.
Ruby: NameError: undefined local variable or method 'x' for main:Object
Ruby saw a bare identifier that is neither a local variable nor a method on the current object.
Rails: ActiveRecord::StaleObjectError: Attempted to update a stale object: Order
Two users/processes updated the same record; the second save failed the `lock_version` check.
Rails: ActiveModel::ForbiddenAttributesError
You passed raw `params` to `new/create/update`, but strong parameters require permitting attributes first.
Rails: ActionController::ParameterMissing: param is missing or the value is empty: user
`params.require(:user)` found no `user` key (or it was blank), so Rails responds 400.
Rails: ActionController::UnknownFormat — UsersController#show is missing a template for this request format and variant
The controller has no template or `respond_to` handler for the requested format (HTML/JSON/etc.).
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