1.查詢(xún)語(yǔ)句通用格式:
SELECT 字段名1[AS 別名],字段名2[AS 別名], ...
FROM 表名
[WHERE 條件]
[GROUP BY 字段]
[HAVING 條件(聚合函數(shù))]
[ORDER BY 字段 DESC|ASC]
[LIMIT 起始序號(hào),記錄條數(shù)]
2.分頁(yè)
LIMIT 起始序號(hào),記錄條數(shù) //起始序號(hào)從0開(kāi)始
SELECT * FROM employee LIMIT 0,5;
3.分頁(yè)原理 - 底層實(shí)現(xiàn)過(guò)程
1> 根據(jù)當(dāng)前頁(yè)號(hào)currentNO 返回相應(yīng)記錄祟敛。 假設(shè)每頁(yè)pageSize條數(shù)據(jù)
currentNo = 1;
SELECT * FROM employee LIMIT (currentNo-1)*pageSize,pageSize;
2>邊界檢查
求總頁(yè)數(shù)?
2.1先求總記錄條數(shù) totalCount ？
SELECT COUNT(*) FROM employee;
2.2 pageNO總頁(yè)數(shù)
if(totalCount%pageSize == 0 ){
pageNO = totalCount/pageSize;
}else{
pageNO = totalCount/pageSize + 1;
}
首頁(yè) currentNo =1;
尾頁(yè) currentNo = pageNO;
下一頁(yè)
currentNo++;
if(currentNo > pageNO){
alert("已經(jīng)到尾頁(yè)");
return;
}
上一頁(yè)
currentNo--;
if(currentNo <= 0){
alert("已經(jīng)到首頁(yè)");
return;
} 