SQL構文の理解


DISTINCT
  • の重複除外に使用します.SELECTオプション
  • SELECT DISTINCT collunm
    FROM ~
    WHERE ~;
    CONVERTCONVERT(expr,type), CONVERT(expr USING transcoding_name)
  • データ型を変換するための
  • // 소숫점이 나오지 않도록 signed int로 형변환
    SELECT CONVERT(AVG(collunm), SIGNED INTEGER) AS 'alias'
    FROM ~
    WHERE ~;
    DATE_ADDDATE_ADD(date,INTERVAL expr unit)算術演算
  • の日付の
  • SELECT DATE_ADD('2000-12-31 23:59:59', INTERVAL 1 SECOND);
    //2001-01-01 00:00:00
    SELECT DATE_ADD('2010-12-31 23:59:59', INTERVAL 1 DAY);
    //2011-01-01 23:59:59
    SELECT DATE_ADD('2100-12-31 23:59:59', INTERVAL '1:1' MINUTE_SECOND);
    //2101-01-01 00:01:00
    SELECT DATE_ADD('1900-01-01 00:00:00', INTERVAL '-1 10' DAY_HOUR);
    //1899-12-30 14:00:00
    SELECT DATE_ADD('1992-12-31 23:59:59.000002', INTERVAL '1.999999' SECOND_MICROSECOND);
    //1993-01-01 00:00:01.000001
    DATEDIFF DATEDIFF(expr1,expr2)
  • の2日間の差異を計算した.は、expr1 - expr2を返し、Day以上の値のみを計算します.
  • SELECT DATEDIFF('2007-12-31 23:59:59','2007-12-30');
    //1
    SELECT DATEDIFF('2010-11-30 23:59:59','2010-12-31');
    //-31
    整理する
    SELECT DISTINCT 
    	CONVERT(
    		DATE_ADD('2021-04-10 23:59:59', INTERVAL 5 DAY), DATE
    	) 
    	AS RecordingDate
    FROM recordmediaindexasoneday
    WHERE