Inserting rows of data into a table

Available in

DSQL, ESQL, PSQL

Syntax

Description

• If the column values are supplied in a VALUES clause, exactly one row is inserted

• The values may be provided instead by a SELECT expression, in which case zero to many rows may be inserted

• With the DEFAULT VALUES clause, no values are provided at all and exactly one row is inserted.

6.2.1. INSERT …​ VALUES

The list must provide a value for every column in the column list, in the same order and of the correct type. The column list need not specify every column in the target but, if the column list is absent, the engine requires a value for every column in the table or view (computed columns excluded).

Examples

INSERT INTO cars (make, model, year)
VALUES ('Ford', 'T', 1908);
INSERT INTO cars
VALUES ('Ford', 'T', 1908, 'USA', 850);
-- notice the '_' prefix (introducer syntax)
INSERT INTO People

6.2.2. INSERT …​ SELECT

For this method of inserting, the output columns of the SELECT statement must provide a value for every target column in the column list, in the same order and of the correct type.

Literal values, context variables or expressions of compatible type can be substituted for any column in the source row. In this case, a source column list and a corresponding VALUES list are required.

If the column list is absent — as it is when SELECT * is used for the source expression — the column_list must contain the names of every column in the target table or view (computed columns excluded).

Examples

Of course, the column names in the source table need not be the same as those in the target table. Any type of SELECT statement is permitted, as long as its output columns exactly match the insert columns in number, order and type. Types need not be exactly the same, but they must be assignment-compatible.

The “Unstable Cursor” Problem

In Firebird, up to and including Firebird 2.5, it is necessary to be aware of an implementation fault that affects this style of inserts when the objective is to duplicate rows in the same table. For example,

INSERT INTO T
  SELECT * FROM T;

This is a quirk that affects all data-changing DML operations, with a variety of effects. It happens because, in the execution layers, DML statements use implicit cursors for performing the operations. Thus, using our simple example, execution works as follows:

The implementation results in behaviour that does not accord with the SQL standards. Future versions of Firebird will comply with the standard.

6.2.3. INSERT …​ DEFAULT VALUES

The DEFAULT VALUES clause allows insertion of a record without providing any values at all, either directly or from a SELECT statement. This is only possible if every NOT NULL or ed column in the table either has a valid default declared or gets such a value from a BEFORE INSERT trigger. Furthermore, triggers providing required field values must not depend on the presence of input values.

Example

INSERT INTO journal
  DEFAULT VALUES
RETURNING entry_id;

6.2.4. The RETURNING clause

An INSERT statement adding at most one row may optionally include a RETURNING clause in order to return values from the inserted row. The clause, if present, need not contain all of the insert columns and may also contain other columns or expressions. The returned values reflect any changes that may have been made in BEFORE INSERT triggers.

Examples

Notes

• RETURNING is only supported for VALUES inserts and singleton SELECT inserts.

• In DSQL, a statement with a RETURNING clause always returns exactly one row. If no record was actually inserted, the fields in this row are all NULL. This behaviour may change in a later version of Firebird. In PSQL, if no row was inserted, nothing is returned, and the target variables keep their existing values.

6.2.5. Inserting into BLOB columns

Inserting into BLOB columns is only possible under the following circumstances:

1. The client application has made special provisions for such inserts, using the Firebird API. In this case, the modus operandi is application-specific and outside the scope of this manual.

2. The value inserted is a text string of no more than 32767 bytes.

   If the value is not a string literal, beware of concatenations, as the output from the expression may exceed the maximum length.