<para>

The general syntax of a variable declaration is:

<synopsis>

<replaceable>name</replaceable> <optional> CONSTANT </optional> <replaceable>type</replaceable> <optional> COLLATE <replaceable>collation_name</replaceable> </optional> <optional> NOT NULL </optional> <optional> { DEFAULT | := } <replaceable>expression</replaceable> </optional>;

<replaceable>name</replaceable> <optional> CONSTANT </optional> <replaceable>type</replaceable> <optional> COLLATE <replaceable>collation_name</replaceable> </optional> <optional> NOT NULL </optional> <optional> { DEFAULT | :=| =} <replaceable>expression</replaceable> </optional>;

</synopsis>

The <literal>DEFAULT</> clause, if given, specifies the initial value assigned

to the variable when the block is entered. If the <literal>DEFAULT</> clause

is specified, an assignment of a null value results in a run-time

error. All variables declared as <literal>NOT NULL</>

must have a nonnull default value specified.

Equals (<literal>=</>) can be used instead of PL/SQL-compliant

<literal>:=</>.

</para>

<para>

An assignment of a value to a <application>PL/pgSQL</application>

variable is written as:

<synopsis>

<replaceable>variable</replaceable>:= <replaceable>expression</replaceable>;

<replaceable>variable</replaceable>{ := | = } <replaceable>expression</replaceable>;

</synopsis>

As explained previously, the expression in such a statement is evaluated

by means of an SQL <command>SELECT</> command sent to the main

database engine. The expression must yield a single value (possibly

a row value, if the variable is a row or record variable). The target

variable can be a simple variable (optionally qualified with a block

name), a field of a row or record variable, or an element of an array

that is a simple variable or field.

that is a simple variable or field. Equals (<literal>=</>) can be

used instead of PL/SQL-compliant <literal>:=</>.

</para>

<para>

command, which has the form:

<synopsis>

GET <optional> CURRENT </optional> DIAGNOSTICS <replaceable>variable</replaceable>= <replaceable>item</replaceable> <optional> , ... </optional>;

GET <optional> CURRENT </optional> DIAGNOSTICS <replaceable>variable</replaceable>{ = | := } <replaceable>item</replaceable> <optional> , ... </optional>;

</synopsis>

This command allows retrieval of system status indicators. Each

<acronym>SQL</acronym> command. Note that <varname>RESULT_OID</>

is only useful after an <command>INSERT</command> command into a

table containing OIDs.

Equals (<literal>:=</>) can be used instead of SQL-standard

<literal>=</> for <command>GET DIAGNOSTICS</>.

</para>

<para>

<command>GET STACKED DIAGNOSTICS</command> command, which has the form:

<synopsis>

GET STACKED DIAGNOSTICS <replaceable>variable</replaceable>= <replaceable>item</replaceable> <optional> , ... </optional>;

GET STACKED DIAGNOSTICS <replaceable>variable</replaceable>{ = | := } <replaceable>item</replaceable> <optional> , ... </optional>;

</synopsis>

Each <replaceable>item</replaceable> is a key word identifying a status

<para>

<synopsis>

GET <optional> CURRENT </optional> DIAGNOSTICS <replaceable>variable</replaceable>= <replaceable>PG_CONTEXT</replaceable> <optional> , ... </optional>;

GET <optional> CURRENT </optional> DIAGNOSTICS <replaceable>variable</replaceable>{ = | := } <replaceable>PG_CONTEXT</replaceable> <optional> , ... </optional>;

</synopsis>

| K_DEFAULT

;

assign_operator:'='/* not documented because it might be removed someday*/

assign_operator:'='

| COLON_EQUALS

;