UPDATE

UPDATE changes the values of the specified columns in all rows that satisfy the condition. More about UPDATE statement can be found at:
PostgreSQL - https://www.postgresql.org/docs/11/sql-update.html
MySQL - https://dev.mysql.com/doc/refman/8.0/en/update.html
MariaDB - https://mariadb.com/kb/en/library/update/

Following clauses are supported:

• UPDATE(columns...) - list of columns to update
• SET(values...) - list of values for columns
• MODEL(model) - list of values for columns will be extracted from model object
• WHERE(condition) - only rows for which condition returns true will be updated.
• FROM(tables...) - table expression allowing columns from other tables to appear in the WHERE condition and update expressions. (postgres, sqlite)
• RETURNING(output_expression...) - expressions to be computed and returned by the UPDATE statement after each row is updated. Expressions can use any column names of the table. (postgres, sqlite)

Example

// replace all Bing links with Yahoo
updateStmt := Link.UPDATE(Link.Name, Link.URL).
    SET("Yahoo", "http://yahoo.com").
    WHERE(Link.Name.EQ(String("Bing")))

// OR using type-safe SET (recommended)
updateStmt := Link.UPDATE().
    SET(
        Link.Name.SET(String("Yahoo")),
        Link.URL.SET(String("http://yahoo.com")),
    ).
    WHERE(Link.Name.EQ(String("Bing")))

Debug sql of above statement:

UPDATE test_sample.link          -- 'test_sample' is name of the schema
SET (name, url) = ('Yahoo', 'http://yahoo.com')
WHERE link.name = 'Bing';

Short-hand notation to update values from model data:

yahoo := model.Link{
    URL:  "http://www.yahoo.com",
    Name: "Yahoo",
}

updateStmt := Link.
    UPDATE(Link.Name, Link.URL, Link.Description).
    MODEL(yahoo).
    WHERE(Link.Name.EQ(String("Bing")))

Link.Name, Link.URL, Link.Description - can be replaced with Link.MutableColumns(all columns minus primary key column).
Primary key columns usually are not updated.

updateStmt := Link.
    UPDATE(Link.MutableColumns).
    MODEL(yahoo).
    WHERE(Link.Name.EQ(String("Bing")))

Execute statement

To execute update statement and get sql.Result:

res, err := updateStmt.Exec(db)

To execute PostgreSQL update statement and return row records updated, statement has to have RETURNING clause:

updateStmt := Link.
    UPDATE(Link.MutableColumns).
    MODEL(yahoo).
    WHERE(Link.Name.EQ(String("Bing"))).
    RETURNING(Link.AllColumns)
    
dest := []model.Link{}

err := updateStmt.Query(db, &dest)   

Use ExecContext and QueryContext to provide context object to execution.

SQL table used for the example:

CREATE TABLE IF NOT EXISTS link (
    id serial PRIMARY KEY,
    url VARCHAR (255) NOT NULL,
    name VARCHAR (255) NOT NULL,
    description VARCHAR (255)
);