custom-expressions.md

Custom Expressions

Custom expressions have to be of type Expr<>

For example,

//RAND()
const myRand = new sql.Expr(
    {
        usedRef : {},
        assertDelegate : dataType.double(),
    },
    new sql.FunctionCall(
        "RAND",
        []
    )
);

//RAND() + 1
const sum = sql.add(myRand, 1);

The above,

• Does not refer to any columns
• Has return type number/DOUBLE
• Is the SQL string RAND()

---

You may also return Expr<> from functions,

function addOne (x : number) {
    return new sql.Expr(
        {
            usedRef : {},
            assertDelegate : dataType.double(),
        },
        [
            RawExprUtil.queryTree(x),
            "+",
            "1e0"
        ]
    );
}

//1 + 1e0
const _2 = addOne(1);
//2 + 1e0
const _3 = addOne(2);

//(1 + 1e0) + (2 + 1e0)
const _5 = sql.add(_2, _3);