Base Grammar SELECT columns FROM tableName WHERE conditions GROUP BY columns HAVING conditions ORDER BY columns LIMIT numbers
Month: August 2024
6. DML – Data Manipulation Language
Add Data — Add data for fixed columns. INSERT INTO tableName (column1,column1,…) VALUES(value1,value2,…); — Add data for whole columns INSERT… Read more
5. Mysql – Date and Time Data Types
Date and Time Data Types Data type Description DATE A date. Format: YYYY-MM-DD. The supported range is from ‘1000-01-01’ to… Read more
4. Mysql – Numeric Data Types
Numeric Data Types BIT(size) A bit-value type. The number of bits per value is specified in size. The size parameter… Read more
3. Mysql – String Data Types
String Data Types Date Type Description CHAR(size) A FIXED length string (can contain letters, numbers, and special characters). The size… Read more
About byte size in real memory
1 byte = 8 bits; 1 byte = 0xFF;
React using “use-immer”
Using immer to manage object. import React from "react"; import { useImmer } from "use-immer"; function App() { const [person,… Read more
React how to call child function?
Use the "useImperativeHandle" Parent file: import {useRef,useEffect} from 'react' import RankingPopup from '@/components/popups/Ranking' export default function(){ const RankingPopupRef = useRef(null)… Read more
How to detect if a div is scrolled to bottom?
Code document.querySelector('.list').addEventListener('scroll',function(e){ // console.log(e.target.scrollTop) // console.log(e.target.clientHeight) // console.log(e.target.scrollHeight) // console.log(Math.abs(e.target.scrollHeight – (e.target.scrollTop + e.target.clientHeight))) if(Math.abs(e.target.scrollHeight – (e.target.scrollTop + e.target.clientHeight)) <… Read more
2. DDL – Data Definition Language
1. Database operation — The "[xxx]" are optional. — Show all databases SHOW DATABASES; — show current database you used…. Read more