mysql和oracle用法的區別

一、分頁

mysql：

select * from table limit m;  --查詢m行

select * from table limit m, n;  --查詢m+n行，撇去前面的m行，返回最後的n行

select * from table limit n offset m;

select * from table where id > 100 limit 0, 10; --第101~110行

oracle：

select * from (select T1.*, rownum rn from (select * from table) T1 where rownum <= 110) where rn > 100;

二、batchUpdateOrInsert

oracle：

<update id="batchUpdateOrInsert" parameterType="map">
        merge into tabel T1
        using (<foreach collection="inList" item="item" index="index" separator="union">
        SELECT
        #{item.XX1} XX1,
        #{item.XX2} XX2,
        FROM DUAL
    </foreach>
        ) T2 on (T1.XX1 = T2.XX1)
        when matched then
        update set
        T1.XX2 = T2.XX2,
        T1.update_date = to_date(#{now}, 'yyyy-mm-dd hh24:mi:ss')
        when not matched then
        insert (ID, XX1, XX2, update_date)
        values (SEQ_TABLE_ID.nextval, T2.XX1, T2.XX2, to_date(#{now}, 'yyyy-mm-dd hh24:mi:ss'))
    </update>

by the way,oracle建表,須要對自增主鍵另外建序列

CREATE TABLE A
(
  ID NUMBER(8,0) NOT NULL 
, USER_MOBILE VARCHAR2(11) NOT NULL 
, CREATE_DATE DATE NOT NULL 
, CREATE_BY VARCHAR2(32) NOT NULL 
, UPDATE_DATE DATE NOT NULL 
, UPDATE_BY VARCHAR2(32) NOT NULL 
, CONSTRAINT A_PK PRIMARY KEY 
  (
    ID 
  )
  ENABLE 
);
COMMENT ON COLUMN A.ID IS '主鍵';

COMMENT ON COLUMN A.USER_MOBILE IS '會員帳號';

--建立序列
create sequence SEQ_A_ID
minvalue 1
maxvalue 9999999999999999999999999999
start with 1
increment by 1
nocache;

mysql：Todo

三、oracle：select 1 from dual;

mysql：select 1;

四、結合mybatis，插入後返回主鍵

oracle單條能夠返回，批量多條不能返回。

<insert id="insertA" parameterType="com.XX.XXmodel">
        <selectKey resultType="java.lang.Integer" keyProperty="id" order="BEFORE">
            select SEQ_A_ID.nextval from dual
        </selectKey>
        insert into A
        <trim prefix="(" suffix=")" suffixOverrides=",">
            ID,
            <if test="userId != null and userId !=''">
                USER_ID,
            </if>
            <if test="changeType != null and changeType !=''">
                CHANGE_TYPE,
            </if>
            <if test="updateDate != null">
                UPDATE_DATE,
            </if>
        </trim>
        <trim prefix="values (" suffix=")" suffixOverrides=",">
            #{id,jdbcType=DECIMAL},
            <if test="userId != null and userId !=''">
                #{userId,jdbcType=DECIMAL},
            </if>
            <if test="changeType != null and changeType !=''">
                #{changeType,jdbcType=VARCHAR},
            </if>
            <if test="updateDate != null">
                #{updateDate,jdbcType=TIMESTAMP},
            </if>
        </trim>
    </insert>

插入後，XXmodel.getId()能夠獲得主鍵id。

<insert id="insertBatchA" parameterType="java.util.List">
        <selectKey resultType="java.lang.Integer" keyProperty="id" order="BEFORE">
            select SEQ_A_ID.nextval from dual
        </selectKey>
        insert into A
        (ID, USER_ID, CHANGE_TYPE, UPDATE_DATE)
        select SEQ_A_ID.nextval, A.* from
        (
        <foreach collection="list" item="item" index="index"
                 separator="union all">
            select
            #{item.userId,jdbcType=DECIMAL},
            #{item.changeType,jdbcType=VARCHAR},
            #{item.updateDate,jdbcType=TIMESTAMP}
            FROM DUAL
        </foreach>
        ) A
    </insert>

oracle單條，批量多條均可以返回。Todo