DB Migration

null 값

  1. Java Code 
    String ctxKey = ...;
Object value = ctx.get(ctxKey);
Object bindingValue = null;
if ( value == null ) {
    bindingValue = value;
} else if ( value instanceof String[] ) {
    String v = ((String[]) value)[0];
    if ( v == null || v.length()==0 ) {
        bindingValue = null;
    } else {
        bindingValue = v;
    }
} else if ( value instanceof String ) {
    String v = ((String) value);
    if ( v == null || v.length()==0 ) {
        bindingValue = null;
    } else {
        bindingValue = v;
    }
} else{
    bindingValue = value;
}

SQL 문

  1. alias 
    List<Map> rowSet = dao.find("emp.select");
//rowSet 을 json data로 변환함
    • Oracle 
      select EMPNO, ENAME, JOB, HIREDATE, DEPTNO from EMP
    • PostgreSQL 
      select EMPNO "EMPNO", ENAME "ENAME", JOB "JOB", HIREDATE "HIREDATE", DEPTNO "DEPTNO" from EMP
      1. nvl
        • Oracle 
          select EMPNO, nvl(ENAME,'unknown') ENAME, JOB, HIREDATE, DEPTNO from EMP
        • PostgreSQL 
          select EMPNO, coalesce(ENAME,'unknown') ENAME, JOB, HIREDATE, DEPTNO from EMP
          1. timestamp + 3
            • Oracle 
              select * from SCHEDULE_JOB_HISTORY where LOG_TIME < CURRENT_TIMESTAMP - 10
            • PostgreSQL 
              select * from SCHEDULE_JOB_HISTORY where LOG_TIME < CURRENT_TIMESTAMP - interval '10 days'
              1. sysdate
                • Oracle 
                  select * from EMP where HIREDATE > sysdate - 30
                • PostgreSQL 
                  select * from EMP where HIREDATE > current_date - 30