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Expression
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expression
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::= expression_item | expression_item { + | - | * | / } expression_item
Note Spaces on each side of the operator are optional.
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expression_item
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::= [ + | - ] { value | column_identifier | function | case_expression | cast_expression | ( expression ) }
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value
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::= literal | USER | variable
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function
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::= set_function | null_function | string_function |
numeric_function |
datetime_function | system_function |
datatypeconversion_function
Note The string, numeric, datetime, and datatype conversion functions are scalar functions in which an operation denoted by a function name is followed by a pair of parenthesis enclosing zero or more specified arguments. Each scalar function returns a single value.
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set_function
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::= COUNT (*) |
{ AVG | MAX | MIN | SUM | COUNT } ( { ALL | DISTINCT } expression ) |
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null_function
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::= { NULLVAL_CHAR( ) | NULLVAL_INT( ) }
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datatypeconversion_function
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::= CONVERT_CHAR(value_exp) | CONVERT_DATE(value_exp) | CONVERT_DECIMAL(value_exp) | CONVERT_DOUBLE(value_exp) | CONVERT_FLOAT(value_exp) | CONVERT_INTEGER(value_exp) | CONVERT_LONGVARCHAR(value_exp) | CONVERT_NUMERIC(value_exp) | CONVERT_REAL(value_exp) | CONVERT_SMALLINT(value_exp) | CONVERT_TIME(value_exp) | CONVERT_TIMESTAMP(value_exp) | CONVERT_TINYINT(value_exp) | CONVERT_VARCHAR(value_exp)
Note These functions are used to implement the {fn CONVERT(value, odbc_typename)} escape clauses defined by ODBC. However, you should use CAST(value AS sql_typename) which is defined in SQL-92 and fully supported by solidDB®.
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case_expression
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::= case_abbreviation | case_specification
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case_abbreviation
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::= NULLIF(value_exp, value_exp) | COALESCE(value_exp {, value_exp }...)
The NULLIF function returns NULL if the first parameter is equal to the second parameter; otherwise, it returns the first parameter. It is equivalent to IF (p1 = p2) THEN RETURN NULL ELSE RETURN p1; The NULLIF function is useful if you have a special value that serves as a flag to indicate NULL. You can use NULLIF to convert that special value to NULL. In other words, it behaves like IF (p1 = NullFlag) THEN RETURN NULL ELSE RETURN p1;
COALESCE returns the first non-NULL argument. The list of arguments may be of almost any length. All arguments should be of the same (or compatible) data types.
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case_specification
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::= CASE [value_exp]
WHEN value_exp THEN {value_exp } [WHEN value_exp THEN { value_exp } ...] [ELSE { value_exp }] END |
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cast_expression
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::= CAST (value_exp AS -data-type)
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row value constructor expression
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A row value constructor (RVC) is an ordered sequence of values delimited by parentheses, for example:
(1, 4, 9)
('Smith', 'Lisa') A row construction is based on a series of elements/values, similar to a row of a table that is composed of a series of fields.
For more information about row value constructors, see Row value constructors.
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