Categories
react.js

React.js: the basics

Basic element creation:

ReactDOM.render(React.createElement('h1', null, 'Hello world!'),document.getElementById('content'))

The first argument, the element
The second: the data to be feed to that element
The third, the innerHTML inside that element

ReactDOM.render does the actual appending to the page



React Hooks
Example (look ma' no classes!):

const GeneralStats = () => {

useEffect(() => {
     // fetch your data or whatever you did on react before hooks here, useEffect is similar to componentdidmount
});

    return (
        <div className="Home">
            Please wait, loading ... 
        </div>
    );

}


export default GeneralStats;

Categories
redshift

Redshift: alter table column TYPE is not allowed

Only allowed for varchar column types.

The trick to get it done:

ALTER TABLE sometable ADD COLUMN some_new_column (with the new definition you want)
UPDATE sometable SET some_new_column = old_column;
ALTER TABLE sometable DROP COLUMN old_column;
ALTER TABLE sometable RENAME COLUMN some_new_column TO old_column;

The catch: column order will be altered (the new column will be the last now

If you use copy to fill out that table, you can’t reorder columns to make it fit still

If that is your setup, instead of create a new column, create a new table with the right TYPE, and do as above