SQL之运算符操作

除此之外，还可以直接对表中的属性进行操作：

<span style="color: #0000ff;">SELECT</span> ename 雇员,sal  月工资,sal<span style="color: #808080;">*</span><span style="color: #800000; font-weight: bold;">12</span><span style="color: #000000;"> 年薪
    </span><span style="color: #0000ff;">FROM</span> t_employee;

 比较运算符：

如果符合条件，返回1，否则返回0；

<span style="color: #0000ff;">SELECT</span> <span style="color: #800000; font-weight: bold;">1</span><span style="color: #808080;">=</span><span style="color: #800000; font-weight: bold;">1</span><span style="color: #000000;">   数值比较,
    </span><span style="color: #ff0000;">‘</span><span style="color: #ff0000;">cjgong</span><span style="color: #ff0000;">‘</span><span style="color: #808080;">=</span><span style="color: #ff0000;">‘</span><span style="color: #ff0000;">cjgong</span><span style="color: #ff0000;">‘</span><span style="color: #000000;"> 字符串比较,
    </span><span style="color: #800000; font-weight: bold;">1</span><span style="color: #808080;">+</span><span style="color: #800000; font-weight: bold;">2</span><span style="color: #808080;">=</span><span style="color: #800000; font-weight: bold;">3</span><span style="color: #808080;">+</span><span style="color: #800000; font-weight: bold;">3</span><span style="color: #000000;"> 表达式比较,
    </span><span style="color: #800000; font-weight: bold;">1</span><span style="color: #808080;"><=></span><span style="color: #800000; font-weight: bold;">1</span><span style="color: #000000;">   数值比较,
    </span><span style="color: #ff0000;">‘</span><span style="color: #ff0000;">cjgong</span><span style="color: #ff0000;">‘</span><span style="color: #808080;"><=></span><span style="color: #ff0000;">‘</span><span style="color: #ff0000;">cjgong</span><span style="color: #ff0000;">‘</span><span style="color: #000000;"> 字符串比较,
    </span><span style="color: #800000; font-weight: bold;">1</span><span style="color: #808080;">+</span><span style="color: #800000; font-weight: bold;">2</span><span style="color: #808080;"><=></span><span style="color: #800000; font-weight: bold;">3</span><span style="color: #808080;">+</span><span style="color: #800000; font-weight: bold;">3</span> 表达式比较;

除此之外可以在where语句中使用：

逻辑运算符：在where中用逻辑运算可以进行条件组合。

真和NULL与还是NULL

<span style="color: #0000ff;">SELECT</span> <span style="color: #800000; font-weight: bold;">3</span> <span style="color: #808080;">AND</span> <span style="color: #800000; font-weight: bold;">4</span><span style="color: #000000;">,
    </span><span style="color: #800000; font-weight: bold;">0</span> <span style="color: #808080;">AND</span> <span style="color: #800000; font-weight: bold;">4</span><span style="color: #000000;">,
    </span><span style="color: #800000; font-weight: bold;">0</span> <span style="color: #808080;">AND</span> <span style="color: #0000ff;">NULL</span><span style="color: #000000;">,
    </span><span style="color: #800000; font-weight: bold;">3</span> <span style="color: #808080;">AND</span> <span style="color: #0000ff;">NULL</span><span style="color: #000000;">,
    </span><span style="color: #800000; font-weight: bold;">3</span> <span style="color: #808080;">&&</span> <span style="color: #800000; font-weight: bold;">4</span><span style="color: #000000;">,
    </span><span style="color: #800000; font-weight: bold;">0</span> <span style="color: #808080;">&&</span> <span style="color: #800000; font-weight: bold;">4</span><span style="color: #000000;">,
    </span><span style="color: #800000; font-weight: bold;">0</span> <span style="color: #808080;">&&</span> <span style="color: #0000ff;">NULL</span><span style="color: #000000;">,
    </span><span style="color: #800000; font-weight: bold;">3</span> <span style="color: #808080;">&&</span> <span style="color: #0000ff;">NULL</span>;

<span style="color: #0000ff;">SELECT</span>  filed <span style="color: #0000ff;">from</span> table_name <span style="color: #0000ff;">where</span> col1<span style="color: #808080;">=</span>x <span style="color: #808080;">and</span> col2 <span style="color: #808080;">=</span>x <span style="color: #808080;">or</span> col3<span style="color: #808080;">></span><span style="color: #800000; font-weight: bold;">10</span>

 位运算符：

bin函数可以查看二进制：

<span style="color: #0000ff;">SELECT</span> <span style="color: #800000; font-weight: bold;">5</span><span style="color: #808080;">&</span><span style="color: #800000; font-weight: bold;">6</span> , BIN(<span style="color: #800000; font-weight: bold;">5</span><span style="color: #808080;">&</span><span style="color: #800000; font-weight: bold;">6</span><span style="color: #000000;">) 二进制数,
    </span><span style="color: #800000; font-weight: bold;">4</span><span style="color: #808080;">&</span><span style="color: #800000; font-weight: bold;">5</span><span style="color: #808080;">&</span><span style="color: #800000; font-weight: bold;">6</span>,BIN(<span style="color: #800000; font-weight: bold;">4</span><span style="color: #808080;">&</span><span style="color: #800000; font-weight: bold;">5</span><span style="color: #808080;">&</span><span style="color: #800000; font-weight: bold;">6</span>) 二进制数;

<span style="color: #0000ff;">SELECT</span> <span style="color: #800000; font-weight: bold;">3</span> XOR <span style="color: #800000; font-weight: bold;">4</span><span style="color: #000000;">,
    </span><span style="color: #800000; font-weight: bold;">0</span> XOR <span style="color: #800000; font-weight: bold;">0</span><span style="color: #000000;">,
    </span><span style="color: #0000ff;">NULL</span> XOR <span style="color: #0000ff;">NULL</span><span style="color: #000000;">,
    </span><span style="color: #800000; font-weight: bold;">0</span> XOR <span style="color: #800000; font-weight: bold;">4</span><span style="color: #000000;">,
    </span><span style="color: #800000; font-weight: bold;">0</span> XOR <span style="color: #0000ff;">NULL</span><span style="color: #000000;">,
    </span><span style="color: #800000; font-weight: bold;">3</span> XOR <span style="color: #0000ff;">NULL</span>;

NULL和任何数据XOR返回NULL

SQL之运算符操作

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