#Alter table add column plus#
n_distinct affects the statistics for the table itself, while n_distinct_inherited affects the statistics gathered for the table plus its inheritance children.
Currently, the only defined per-attribute options are n_distinct and n_distinct_inherited, which override the number-of-distinct-values estimates made by subsequent ANALYZE operations. This form sets or resets per-attribute options.
#Alter table add column update#
SET STATISTICS acquires a SHARE UPDATE EXCLUSIVE lock.
For more information on the use of statistics by the PostgreSQL query planner, refer to Section 14.2. The target can be set in the range 0 to 10000 alternatively, set it to -1 to revert to using the system default statistics target ( default_statistics_target). This form sets the per-column statistics-gathering target for subsequent ANALYZE operations. sequence_option is an option supported by ALTER SEQUENCE such as INCREMENT BY. These forms alter the sequence that underlies an existing identity column. If DROP IDENTITY IF EXISTS is specified and the column is not an identity column, no error is thrown. Like SET DEFAULT, these forms only affect the behavior of subsequent INSERT and UPDATE commands they do not cause rows already in the table to change. These forms change whether a column is an identity column or change the generation attribute of an existing identity column. RENAME CONSTRAINT constraint_name TO new_constraint_nameĪLTER TABLE ALL IN TABLESPACE name ]ĪTTACH PARTITION partition_name AS IDENTITY | 1 | Ramesh | 32 | Ahmedabad | 2000.ALTER TABLE name Now, the CUSTOMERS table is changed and following would be the output from the SELECT statement. | 7 | Muffy | 24 | Indore | 10000.00 | NULL |įollowing is the example to DROP sex column from the existing table. | ID | NAME | AGE | ADDRESS | SALARY | SEX | Now, the CUSTOMERS table is changed and following would be output from the SELECT statement. | 1 | Ramesh | 32 | Ahmedabad | 2000.00 |įollowing is the example to ADD a New Column to an existing table − The basic syntax of an ALTER TABLE command to DROP PRIMARY KEY constraint from a table is as follows.Ĭonsider the CUSTOMERS table having the following records −
#Alter table add column code#
If you're using MySQL, the code is as follows − The basic syntax of an ALTER TABLE command to DROP CONSTRAINT from a table is as follows. The basic syntax of an ALTER TABLE command to ADD PRIMARY KEY constraint to a table is as follows.ĪDD CONSTRAINT MyPrimaryKey PRIMARY KEY (column1, column2.)
The basic syntax of an ALTER TABLE command to ADD CHECK CONSTRAINT to a table is as follows.ĪDD CONSTRAINT MyUniqueConstraint CHECK (CONDITION) The basic syntax of ALTER TABLE to ADD UNIQUE CONSTRAINT to a table is as follows.ĪDD CONSTRAINT MyUniqueConstraint UNIQUE(column1, column2.) The basic syntax of an ALTER TABLE command to add a NOT NULL constraint to a column in a table is as follows.ĪLTER TABLE table_name MODIFY column_name datatype NOT NULL The basic syntax of an ALTER TABLE command to change the DATA TYPE of a column in a table is as follows.ĪLTER TABLE table_name MODIFY COLUMN column_name datatype The basic syntax of an ALTER TABLE command to DROP COLUMN in an existing table is as follows.ĪLTER TABLE table_name DROP COLUMN column_name The basic syntax of an ALTER TABLE command to add a New Column in an existing table is as follows.ĪLTER TABLE table_name ADD column_name datatype You should also use the ALTER TABLE command to add and drop various constraints on an existing table. The SQL ALTER TABLE command is used to add, delete or modify columns in an existing table.