Basic Syntactical Items

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# Basic Syntactical Items

This document describes basic syntactical items, which are referenced within the individual SQL statement descriptions.

This document covers the following topics:

- Constants

- Names

- Parameters

- Natural Formats and SQL Data Types

## Constants

The constants used in the syntactical descriptions of the Natural SQL statements are:

`constant` | The item `constant` refers to either a Natural constant or an SQL datetime constant.
`integer` | The item `integer` always represents an integer constant.

Note
If the character for decimal point notation (session parameter `DC`) is set to a comma (,), any specified numeric constant must not be followed directly by a comma, but must be separated from it by a blank character; otherwise an error or wrong results occur.

Invalid Syntax: | Valid Syntax:
--- | ---
`VALUES (1,'A')` leads to a syntax error. `VALUES (1,2,3)` leads to wrong results. | `VALUES (1 ,'A')` `VALUES (1 ,2 ,3)`

### SQL Datetime Constants

An SQL datetime constant is a character string constant of a particular format that specifies one of the following:

`DATE string-constant` | Specifies an SQL date constant, for example: `DATE '2013-15-01'`.
`TIME string-constant` | Specifies an SQL time constant, for example: `TIME '10:30:15'`.
`TIMESTAMP string-constant` | Specifies an SQL time stamp constant, for example: `TIMESTAMP '2014-15-01 10:20:15.123456'`.

For information on the valid `string-constant` formats, refer to IBM's Db2 SQL reference information.

## Names

The names used in the syntactical descriptions of the Natural SQL statements are:

- authorization-identifier

- ddm-name

- view-name

- column-name

- location-name

- table-name

- correlation-name

### authorization-identifier

The item `authorization-identifier`, which is also called creator name, is used to qualify database tables and views. See also `authorization-identifier` under table-name below.

### ddm-name

The item `ddm-name` always refers to the name of a Natural data definition module (DDM) as created with the Natural DDM Services.

### view-name

The item `view-name` always refers to the name of a Natural view as defined in the `DEFINE DATA` statement.

### column-name

The item `column-name` always refers to the name of a physical database column.

### location-name

The item `location-name` always denotes the location of the table. Specification of location-name is optional and belongs to the SQL Extended Set.

### table-name

The item `table-name` in this section is used to reference both SQL base tables and SQL viewed tables.

Syntax of item `table-name`:

[[location-name.]authorization-identifier.]ddm-name

Syntax Element Description:

Syntax Element | Description
--- | ---
`ddm-name` | A Natural data definition module (DDM) must have been created for a table to be used. The name of such a DDM must be the same as the corresponding database table name or view name.
`location-name` | This optional item specifies the location of the table to be accessed.
`authorization-identifier` | There are two ways of specifying the `authorization-identifier` of a database table or view. One way corresponds to the standard SQL syntax, in which the `authorization-identifier` is separated from the table name by a period. Using this form, the name of the DDM must be the same as the name of the database table without the `authorization-identifier`. Example:
    DEFINE DATA LOCAL
    01 PERS VIEW OF PERSONNEL
       02 NAME
       02 AGE
    END-DEFINE
    SELECT *
      INTO VIEW PERS
      FROM SQL.PERSONNEL
    ...
Alternatively, you can define the `authorization-identifier` as part of the DDM name. The DDM name then consists of the `authorization-identifier` and the database table name separated by a hyphen (-). The hyphen between the `authorization-identifier` and the table name is converted internally into a period. Note This form of DDM name can also be used with a `FIND` or `READ` statement, because it conforms to the DDM naming conventions applicable to these statements. Example:
    DEFINE DATA LOCAL
    01 PERS VIEW OF SQL-PERSONNEL
       02 NAME
       02 AGE
    END-DEFINE
    SELECT *
      INTO VIEW PERS
      FROM SQL-PERSONNEL
    ...
If the `authorization-identifier` has been specified neither explicitly nor within the DDM name, it is determined by the SQL database system. In addition to being used in `SELECT` statements, table names can also be specified in `DELETE`, `INSERT` and `UPDATE` statements. Examples:
    ...
    DELETE FROM SQL.PERSONNEL
      WHERE AGE IS NULL
     ...

    ...
    INSERT INTO SQL.PERSONNEL (NAME,AGE)
      VALUES ('ADKINSON',35)
    ...

    ...
    UPDATE SQL.PERSONNEL
    SET SALARY = SALARY * 1.1
    WHERE AGE > 30
    ...

### correlation-name

The item `correlation-name` represents an alias name for a `table-name`. It can be used to qualify column names; it also serves to implicitly qualify fields in a Natural view when used with the `INTO` clause of the `SELECT` statement.

Example:

    DEFINE DATA LOCAL
    01 PERS-NAME    (A20)
    01 EMPL-NAME    (A20)
    01 AGE          (I2)
    END-DEFINE
    ...
    SELECT X.NAME , Y.NAME , X.AGE
      INTO PERS-NAME , EMPL-NAME , AGE
      FROM SQL-PERSONNEL X , SQL-EMPLOYEES Y
      WHERE X.AGE = Y.AGE
    END-SELECT
    ...

Although in most cases the use of `correlation-names` is not necessary, they may help to make the statement clearer.

## Parameters

Syntax of item `parameter`:

[`:`] host-variable [`INDICATOR` [`:`] host-variable] [`LINDICATOR` [`:`] host-variable]

Syntax Element Description:

Syntax Element | Description
--- | ---
`host-variable` | A `host-variable` is a Natural user-defined variable (no system variable) which is referenced in an SQL statement. It can be either an individual field or defined as part of a Natural view. When defined as a receiving field (for example, in the `INTO` clause), a `host-variable` identifies a variable to which a value is assigned by the database system. When defined as a sending field (for example, in the `WHERE` clause), a `host-variable` specifies a value to be passed from the program to the database system. See also Natural Formats and SQL Data Types.
`[:]` | Colon: To comply with SQL standards, a `host-variable` can also be prefixed by a colon (:). When used with flexible SQL, `host-variables` must be qualified by colons. Example:
    SELECT NAME INTO :#NAME FROM PERSONNEL
    WHERE AGE = :VALUE
The colon is always required if the variable name is identical to an SQL reserved word. In a context in which either a `host-variable` or a column can be referenced, the use of a name without a colon is interpreted as a reference to a column.
`INDICATOR` | INDICATOR Clause: The `INDICATOR` clause is an optional feature to distinguish between a "null" value (that is, no value at all) and the actual values `0` or "blank". When specified with a receiving `host-variable` (target field), the `INDICATOR host-variable` (null indicator field) serves to find out whether a column to be retrieved is "null". Example:
    DEFINE DATA LOCAL
    1 NAME      (A20)
    1 NAMEIND   (I2)
    END-DEFINE
    SELECT *
      INTO NAME INDICATOR NAMEIND
    ...
In this example, `NAME` represents the receiving `host-variable` and `NAMEIND` the null indicator field. If a null indicator field has been specified and the column to be retrieved is null, the value of the null indicator field is negative and the target field is set to `0` or "blank" depending on its data type. Otherwise, the value of the null indicator field is greater than or equal to `0`. When specified with a sending `host-variable` (source field), the null indicator field is used to designate a null value for this field. Example:
    DEFINE DATA LOCAL
    1 NAME      (A20)
    1 NAMEIND   (I2)
    UPDATE ...
    SET NAME = :NAME INDICATOR :NAMEIND
    WHERE ...
In this example, `:NAME` represents the sending `host-variable` and `:NAMEIND` the null indicator field. By entering a negative value as input for the null indicator field, a null value is assigned to a database column. An `INDICATOR host-variable` is of format/length I2.
`LINDICATOR` | LINDICATOR Clause: The `LINDICATOR` clause is an optional feature which is used to support columns of varying lengths, for example, `VARCHAR` or `LONG VARCHAR` type. When specified with a receiving `host-variable` (target field), the `LINDICATOR host-variable` (length indicator field) contains the number of characters actually returned by the database into the target field. The target field is always padded with blanks. If the `VARCHAR` or `LONG VARCHAR` column contains more characters than fit in the target field, the length indicator field is set to the length actually returned (that is, the length of the target field) and the null indicator field (if specified) is set to the total length of this column. Example
    DEFINE DATA LOCAL
    1 ADDRESSLIND (I2)
    1 ADDRESS     (A50/1:6)
    END-DEFINE
    SELECT *
      INTO :ADDRESS(*) LINDICATOR :ADDRESSLIND
      ...
In this example, `:ADDRESS(*)` represents the target field which receives the first 300 bytes (if available) of the addressed `VARCHAR` or `LONG VARCHAR` column, and `:ADDRESSLIND` represents the length indicator field which contains the number of characters actually returned. When specified with a sending `host-variable` (source field), the length indicator field specifies the number of characters of the source field which are to be passed to the database. Example:
    DEFINE DATA LOCAL
    1 NAMELIND  (I2)
    1 NAME      (A20)
    1 AGE       (I2)
    END-DEFINE
    MOVE  4     TO NAMELIND
    MOVE 'ABC%' TO NAME
    SELECT AGE
      INTO :AGE
    WHERE NAME LIKE :NAME LINDICATOR :NAMELIND
      ...
A `LINDICATOR host-variable` is of format/length I2 or I4. For performance reasons, it should be specified immediately before the corresponding target or source field; otherwise, the field is copied to the temporary storage at runtime. If the `LINDICATOR` field is defined as an I2 field, the SQL data type `VARCHAR` is used for sending or receiving the corresponding column. If the `LINDICATOR host-variable` is specified as I4, a large object data type (CLOB/BLOB) is used. If the field is defined as `DYNAMIC`, the column is read in an internal loop up to its real length. The `LINDICATOR` field and `*LENGTH` are set to this length. In case of a fixed length field, the column is read up to the defined length. In both cases, the field is written up to the value defined in the `LINDICATOR` field. Let a fixed length field be defined with a `LINDICATOR` field specified as I2. If the `VARCHAR` column contains more characters than fit into this fixed length field, the length indicator field is set to the length actually returned and the null indicator field (if specified) is set to the total length of this column (retrieval). This is not possible for fixed length fields greater than or equal to 32 KB (length does not fit into null indicator field).

## Natural Formats and SQL Data Types

The Natural data format of a host-variable is converted to an SQL data type according to the following table:

Natural Format/Length | SQL Data Type
--- | ---
`An` | `CHAR (n)`
`B2` | `SMALLINT`
`B4` | `INT`
`Bn`; `n` not equal to 2 or 4 | `CHAR (n)`
`F4` | `REAL`
`F8` | `DOUBLE PRECISION`
`I2` | `SMALLINT`
`I4` | `INT`
`Nnn.m` | `NUMERIC (nn+m,m)`
`Pnn.m` | `NUMERIC (nn+m,m)`
`T` | `TIME`
`D` | `DATE`
`Gn`; for view fields only | `GRAPHIC (n)`

Natural does not check whether the converted SQL data type is compatible to the database column. Except for fields of format N, no data conversion is done.

In addition, the following extensions to standard Natural formats are available with Natural SQL:

- A one-dimensional array of format A can be used to support alphanumeric columns longer than 253 bytes. This array must be defined beginning with index 1 and can only be referenced by using an asterisk (*) as the index. The corresponding SQL data type is `CHAR (n)`, where `n` is the total number of bytes in the array.

- A special `host-variable` indicated by the keyword `LINDICATOR` can be used to support variable-length columns. The corresponding SQL data type is `VARCHAR (n)`; see also the `LINDICATOR` clause.

- The Natural formats date (D) and time (T) can be used with Entire Access and will be converted into the corresponding database-dependent formats (see the Entire Access documentation for details)

A sending field specified as one-dimensional array without a `LINDICATOR` field is converted into the SQL data type `VARCHAR`. The length is the total number of bytes in the array, not taking into account trailing blanks.

### On this page

- Constants
- Names
- Parameters
- Natural Formats and SQL Data Types