Question

比方说，我有一个表，其中包含E_name，DepartmentName，Salary

E_name  DepartmentName  Salary
AAA     D1              1000
BBB     D1              1400
CCC     D2              1320
DDD     D2              1100
EEE     D3              900
FFF     D3              1200

如何向DepartmentName显示其雇员的平均工资高于所有雇员的平均工资

Answer 1

 select dept_name,sal 
 group by dept_name 
 having sal > avg(sal);`

你是这个意思吗？因为这样说，所有部门的所有薪水均高于该部门所有薪水的平均值，即可得出结果。

Answer 2

您可以将All id's exists与GROUP BY子句一起使用

HAVING

Answer 3

我将在按部门分组的聚合查询和未分组的聚合查询之间加入：

import React, { Component } from 'react';
import PropTypes from 'prop-types';
import InputBase from '@material-ui/core/InputBase';
import { withStyles } from '@material-ui/core/styles';
import { withRouter } from 'react-router-dom';
import { connect } from 'react-redux';
import { getAppInfo } from '../../actions/appActions.js';
import constants from '../../constants.js';

import { AppSearchBarInputStyles } from '../styles/Material-UI/muiStyles.js';
import AppNotFound from './AppNotFound.js';

import * as log from 'loglevel';
log.setLevel("debug")


class AppSearchBarInput extends Component {
  state = {
    appId: '',
    snackBarOpen: false
  }

  onChange = e => {
    this.setState({ appId: e.target.value });
  }

  onKeyDown = e => {
    const { appId } = this.state;

    if (e.keyCode === constants.ENTER_KEY) {
      if (appId.trim() !== '') {
        this.props.getAppInfo({ appId });
        this.setState({
          appId: ''
        });

        const { found } = this.props.app; // ! problem here !
        if (found) {
          this.props.history.push('/app/appInfo');
        } else {
          this.setState({
            snackBarOpen: true
          });
        }
      } else {
        this.setState({
          snackBarOpen: true
        });
      }
    }
  }

  handleCloseSnackBar = () => {
    this.setState({
      snackBarOpen: false
    });
  }

  render() {

    const { classes } = this.props;
    const { appId, snackBarOpen } = this.state;
    const { found } = this.props.app;
    let message = '';
    if (!found) {
      message = appId === '' ? constants.MESSAGES.APP_BLANK() : constants.MESSAGES.APP_NOT_FOUND(appId);
    }

    return (
      <div>
        <InputBase
          placeholder="Search…"
          classes={{
            root: classes.inputRoot,
            input: classes.inputInput,
          }}
          onChange={this.onChange}
          onKeyDown={this.onKeyDown}
          value={this.state.appId} />
        <AppNotFound message={message}
                     open={snackBarOpen && !found}
                     onClose={this.handleCloseSnackBar}/>
      </div>
    )
  }
}

AppSearchBarInput.propTypes = {
  classes: PropTypes.object.isRequired
}

const mapStateToProps = state => ({
  app: state.app.app
});

const AppSearchBarWithStyles = withStyles(AppSearchBarInputStyles)(AppSearchBarInput);
const AppSearchBarWithStylesWithRouter = withRouter(AppSearchBarWithStyles);
export default connect(mapStateToProps, { getAppInfo })(AppSearchBarWithStylesWithRouter);

将组的汇总值与整个表的汇总值进行比较

3 个答案: