UPDATE

Syntax 1:

This is the most standard syntax, working with all type of database engines.

UPDATE table-specification
   SET
       column = { variable | sql-expression }
       [,...] 
   [ sql-condition ]

Syntax 2:

This syntax is not standard, but will be converted by the compiler to a portable UPDATE syntax.

UPDATE table-specification 
   SET ( column [,...] )
     = ( { variable | sql-expression } [,...] )
   [ sql-condition ]

Syntax 3:

This syntax is not portable, and is not converted by the compiler.

UPDATE table-specification 
   SET [table.]*
     = ( { variable | sql-expression } [,...] )
   [ sql-condition ]

Syntax 4:

This syntax requires a database schema specification with SCHEMA instruction, and the corresponding database schema file. With this syntax, the columns of record.* are expanded, without the SERIAL or BIGSERIAL column:

UPDATE table-specification 
   SET { [table.]* | ( column [,...] ) }
     = record.*
   [ sql-condition ]

WHERE { condition | CURRENT OF cursor } 

1. dbname identifies the database name.
2. dbserver identifies the database server (INFORMIXSERVER).
3. owner identifies the owner of the table, with optional double quotes.
4. table is the name of the database table.
5. column is a name of a table column.
6. variable is a program variable, a record member or an array member used as a parameter buffer to provide values.
7. sql-expression is an expression supported by the database server, this can be a literal or NULL for example.
8. record is the name of a record (followed by dot star in this syntax).
9. condition is an SQL expression to select the rows to be updated.
10. cursor is the identifier of a database cursor.

Usage

The UPDATE SQL statement can be used to modify one or more rows in the specified database table.

It is recommended to avoid using the dbname, dbserver and owner prefix of the table name to ensure maximum SQL portability.

The third syntax is not standard and will not work with all database types. It is not recommended.

The fourth syntax can be used if the database schema file has been generated with the correct data types. This is especially important when using SERIAL columns or equivalent auto-incremented columns. The fglcomp compiler will automatically extend the SQL text with the columns identified by the record variable. The columns defined in the database schema file as SERIAL or BIGSERIAL will be omitted in the generated column list.

column with a subscript expression (column[a,b]) is not recommended because most database servers do not support this notation.

For more details about the WHERE CURRENT OF clause, see Positioned updates/deletes.