Using the ENUM Data Type

An ENUM is a string value chosen from a user-defined list of values that are specified when creating a table. The values in an ENUM list must be quoted strings, which are distinct from others in the list. A column can be defined as ENUM using the following syntax:

CREATE TABLE table_name (  
    ---  
    col_name ENUM('val1','val2',...,'valN')
)

The values in an ENUM list are indexed, starting from 1. Consider a column defined as mode ENUM('Primary','Secondary','Tertiary'). The following table displays the index for each possible value that the column can have.

The index of a NULL value is NULL. An empty string denotes an invalid value, and it has an index of 0. You can use the following query to identify the rows with invalid ENUM value assignments:

SELECT ...
WHERE enum_column = 0;

ENUM values cannot be expressions or user-defined variables. In non-strict mode, an invalid value is inserted as an empty string. ENUM values are sorted based on their index values. The NULL values are sorted first, then the empty strings (with index 0), followed by the values in the ENUM list.

The following example shows how ENUM values are defined and used.

CREATE ROWSTORE TABLE delivery_status  
(ID VARCHAR(6),    
  Status ENUM('NOT_DISPATCHED','IN_TRANSIT','DELIVERED'));

INSERT INTO delivery_status VALUES('xdy',1);
INSERT INTO delivery_status VALUES('tsg','IN_TRANSIT');
INSERT INTO delivery_status (ID) VALUES('qfc');

SELECT * FROM delivery_status ORDER BY Status ASC;

+------+----------------+
| ID   | Status         |
+------+----------------+
| qfc  | NULL           |
| xdy  | NOT_DISPATCHED |
| tsg  | IN_TRANSIT     |
+------+----------------+

This example shows that if an integer values is specified, the ENUM value at that index is inserted. Because the NOT NULL constraint was not applied on the column, the default value inserted is NULL.

Additional ENUM values can be added or modified to an existing rowstore table using the ALTER TABLE command. To add the additional ENUM values "NOT_SHIPPED" and "RETURNED":

ALTER TABLE delivery_status MODIFY Status ENUM ('NOT_DISPATCHED','IN_TRANSIT','DELIVERED','NOT_SHIPPED','RETURNED');

SHOW CREATE TABLE delivery_status;
+-----------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table           | Create Table                                                                                                                                                                                                                                                                                                                                                                      |
+-----------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| delivery_status | CREATE ROWSTORE TABLE `delivery_status` (  `ID` varchar(3) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,  `Status` enum('NOT_DISPATCHED','IN_TRANSIT','DELIVERED','NOT_SHIPPED','RETURNED') CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL  , SHARD KEY () ) AUTOSTATS_CARDINALITY_MODE=PERIODIC AUTOSTATS_HISTOGRAM_MODE=CREATE SQL_MODE='STRICT_ALL_TABLES' |
+-----------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

Creating an index on an ENUM column on columnstore tables is not supported. Altering the ENUM values via the ALTER TABLE command on columnstore tables is also not supported because the column segments would need to be re-encoded.

To add ENUM values in a columnstore table, there are a couple of workarounds that must be processed offline. See the following examples on how to add the additional ENUM values "NOT_SHIPPED" and "RETURNED" to a columnstore table.

• Create a new table with the updated ENUM values, copy the old table to the new table, drop the old table, and rename the new table with the dropped table's name:

  SQL

  Copy

  -- Existing columnstore table 
  CREATE TABLE delivery_status  
  (ID VARCHAR(6),    
    Status ENUM('NOT_DISPATCHED','IN_TRANSIT','DELIVERED'));
  
  -- Create a new table and add values to the ENUM column 
  CREATE TABLE delivery_status_1  
  (ID VARCHAR(6),    
    Status ENUM('NOT_DISPATCHED','IN_TRANSIT','DELIVERED','NOT_SHIPPED','RETURNED'));
  
  -- Copy the old table to the new table and check to see if the data is correct
  INSERT INTO delivery_status_1(SELECT * FROM delivery_status);
  SELECT * FROM delivery_status_1;
  
  -- Once you are sure the data from the old table has been copied correctly, drop the old table 
  DROP TABLE delivery_status;
  
  -- Rename the new table with dropped table's name 
  ALTER TABLE delivery_status_1 RENAME TO delivery_status;

  If the new ENUM values are not correct after copying the data from the old table to the new table, drop the new table (e.g., delivery_status_1) and repeat the process from the previous code block.

  SQL

  Copy

  DROP TABLE delivery_status_1;

• Add a new column with the updated ENUM values, copy over the values from the old ENUM column to the new ENUM column, drop the old ENUM column, and rename the new ENUMcolumn with the dropped ENUM column's name:

  SQL

  Copy

  -- Existing columnstore table 
  CREATE TABLE delivery_status  
  (ID VARCHAR(6),    
    Status ENUM('NOT_DISPATCHED','IN_TRANSIT','DELIVERED'));
  
  -- Add a new column with updated ENUM values 
  ALTER TABLE delivery_status ADD COLUMN Status1 ENUM ('NOT_DISPATCHED','IN_TRANSIT','DELIVERED','NOT_SHIPPED','RETURNED');
  
  -- Copy values from the old column to the new column and check table to see if the data is correct
  UPDATE delivery_status SET Status = Status1;
  SELECT * FROM delivery_status;
  
  -- Once you are sure the data from the old column have been copied correctly, drop the old column 
  ALTER TABLE delivery_status DROP COLUMN Status;
  
  -- Rename the new column with the dropped column's name 
  ALTER TABLE delivery_status CHANGE Status1 Status;

  If the new ENUM values are not correct after copying the data from the old column to the new column, drop the new column (e.g., Status1) and repeat the process from the previous code block.

  SQL

  Copy

  ALTER TABLE delivery_status DROP COLUMN Status1;

Using the SET Data Type

The SET data type restricts the values that can be inserted for a table column, and can have zero or more string values. However, the string value must exist in the list of values specified for the column at the time of table creation.

A SET column value can contain multiple set members, separated by commas. In such a case,

• the SET member values should not individually contain commas.

• the SET member values can be inserted in any order. The results are retrieved in the same order as listed at the time of table creation.

• even if a SET member value is repeated, the results display the value only once.

The following example displays the usage of the SET data type:

Create a table column with SET data type.

CREATE TABLE setexample (col SET('v1', 'v2', 'v3', 'v4'));

Insert column values as v1,v2, v2,v1, v1,v4,v4, and v3,v4,v3.

INSERT INTO setexample (col) VALUES ('v1,v2'), ('v2,v1'), ('v1,v4,v4'), ('v3,v4,v3');

The result is retrieved in the same order in which the SET member values were listed during table creation and duplicate values are ignored:

SELECT col FROM setexample;

+------------------------------+
| col                          |
+------------------------------+
| v1,v2                        |
| v1,v2                        |
| v1,v4                        |
| v3,v4                        |
+------------------------------+

Using the BIT Data Type

The BIT data type is used to represent bit vectors. It stores bit values in binary notation, i.e., a binary value represented using 0s and 1s. A value of type BIT(n) can store n-bit values, where n can range from 1 to 64. However, SingleStore gives a warning if the size of BIT type column is not 64.

SELECT b'1100101' AS 'String Value', CHARSET(b'1100101') AS 'Charset';

+--------------+---------+
| String Value | Charset |
+--------------+---------+
| e            | binary  |
+--------------+---------+

SELECT b'1100101' + 9;

+----------------+
| b'1100101' + 9 |
+----------------+
|            110 |
+----------------+