Error map
NonUniqueResultException IncorrectResultSizeDataAccessException: query did not return a unique result: 2
Java · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (11). 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 (11)
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
A lazy-loaded association was accessed after the Hibernate session/transaction closed.
MySQL ERROR 1093 (HY000): You can't specify target table 'x' for update in FROM clause
An UPDATE/DELETE uses a subquery that reads from the same table, which MySQL doesn’t allow directly.
ERROR: currval of sequence "x" is not yet defined in this session
currval() was called before nextval() in the same session.
Subquery returns more than 1 row (MySQL 1242) / more than one row returned by a subquery used as an expression
A subquery used where a single value is expected (`= (SELECT …)`) returned several rows.
MySQL ERROR 1175 (HY000): You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
MySQL Workbench’s safe updates mode blocked an UPDATE/DELETE without a key-based WHERE.
MySQL ERROR 1241 (21000): Operand should contain 1 column(s)
A subquery or expression returned several columns where only one is expected.
sqlalchemy.exc.IntegrityError: (psycopg2.errors.UniqueViolation) duplicate key value violates unique constraint
A database constraint (unique, foreign key, not null) rejected an insert/update made through SQLAlchemy.
org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing
An entity references another entity that hasn’t been saved yet, and no cascade is configured.
org.hibernate.exception.ConstraintViolationException: could not execute statement
The database rejected an insert/update because of a constraint (unique, foreign key, not null).
ERROR: could not determine data type of parameter $1
PostgreSQL can’t infer a parameter’s type from context (e.g. $1 IS NULL or SELECT $1).
ERROR: bind message supplies 2 parameters, but prepared statement requires 1
The number of query parameters sent doesn’t match the $1, $2 … placeholders in the SQL.
Two steps away (22)
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class X and no properties discovered
Jackson can’t serialize the class — it has no public getters/fields, or it’s a Hibernate proxy, or Java 8 date types without the…
SequelizeConnectionRefusedError: connect ECONNREFUSED 127.0.0.1:5432
Sequelize couldn’t connect to the database server.
sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) connection to server … failed
SQLAlchemy’s DB driver raised an operational error — connection failures, lost connections or locked SQLite databases.
ERROR: there is no unique or exclusion constraint matching the ON CONFLICT specification
INSERT … ON CONFLICT (cols) names columns that don’t have a matching unique index/constraint.
ERROR: column "x" is of type integer but expression is of type text — HINT: You will need to rewrite or cast the expression.
An INSERT/UPDATE supplies a value of a different type than the column, and PostgreSQL won’t cast implicitly.
PostgreSQL: ERROR: duplicate key value violates unique constraint
An INSERT/UPDATE would create a duplicate in a UNIQUE or PRIMARY KEY column — or the id sequence is behind the existing data.
ERROR: operator does not exist: integer = text
A comparison or operation mixes types PostgreSQL won’t implicitly convert.
MySQL ERROR 1062 (23000): Duplicate entry for key
An INSERT/UPDATE would create a duplicate value in a PRIMARY or UNIQUE key.
Column must appear in the GROUP BY clause / isn't in GROUP BY (MySQL 1055 only_full_group_by)
You selected a column that is neither grouped nor aggregated, so the result would be ambiguous.
InvalidOperationException: Sequence contains no elements / more than one element
LINQ `First()`, `Single()`, `Last()` or `Max()` ran on an empty sequence (or `Single()` found several items).
API Error: Resource already exists (ALREADY_EXISTS / resource_already_exists / 409)
The create request was refused because an object with the same unique identity — name, email, external ID — already exists.
DbUpdateException: An error occurred while saving the entity changes. See the inner exception for details.
SaveChanges failed in the database; the inner exception (SqlException/PostgresException) has the real reason — constraint violati…
Performance: N+1 query problem (one query per row in a loop)
Code runs one query to load a list, then one more query per item — hundreds of queries per page.
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.
PrismaClientKnownRequestError P2002: Unique constraint failed on the fields: (`email`)
A Prisma create/update violated a unique constraint.
ERROR: update or delete on table "users" violates foreign key constraint on table "orders" — Key (id)=(5) is still referenced
You tried to delete a row that other rows still reference.
Blue Screen: IRQL_NOT_LESS_OR_EQUAL (Stop code 0x0000000A)
A driver accessed memory at an interrupt level where that’s not allowed — almost always a faulty or incompatible driver, sometime…
Windows upgrade error 0xC1900101 (driver error, rolled back)
A Windows feature update failed and rolled back because a driver crashed or was incompatible during installation.
Blue screen: DPC_WATCHDOG_VIOLATION (0x00000133)
A driver spent too long at high priority (DPC level) — typically SSD/NVMe firmware, storage controller drivers (iaStorA.sys) or g…
ERROR: current transaction is aborted, commands ignored until end of transaction block
An earlier statement in the same transaction failed; PostgreSQL rejects everything until you ROLLBACK.
ERROR: prepared statement "s1" already exists (PgBouncer transaction mode)
Named prepared statements collided — typically because PgBouncer in transaction pooling mode hands connections between clients.
pg_dump: error: aborting because of server version mismatch
Your pg_dump client is older than the server you’re dumping.
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