我有一个来自the geonames website for Great Britain的数据库转储。它包含大约60000条记录。 示例数据如下：
id | name | admin1 | admin2 | admin3 | feature_class | feature_code
-------------------------------------------------------------------------------------------
2652355 | Cornwall | ENG | C6 | | A | ADM2
11609029 | Cornwall | ENG | | | L | RGN
6269131 | England | ENG | | | A | ADM1
具有功能代码ADM2的第一条记录表示它是管理级别2 特征代码为RGN的secord记录表示它是一个区域。
我想按地名搜索记录以构建自动完成功能。 如果记录具有相同的名称，并且如果其中一个记录是一个区域，即具有feature_code RGN，那么我只想返回该记录 记录，否则我想返回与ID最低的名称匹配的记录。
我尝试了以下操作，但不起作用：
SELECT IF(t0.feature_code = 'RGN', MAX(t0.id), MIN(t0.id)) as id
, CONCAT_WS(', ', t0.name,
IF(t3.name != t0.name, t3.name, NULL),
IF(t2.name != t0.name, t2.name, NULL),
IF(t1.name != t0.name, t1.name, NULL)) AS name
FROM locations t0
LEFT JOIN locations t1 ON t1.admin1 = t0.admin1 AND t1.feature_code = 'ADM1'
LEFT JOIN locations t2 ON t2.admin2 = t0.admin2 AND t2.feature_code = 'ADM2'
LEFT JOIN locations t3 ON t3.admin3 = t0.admin3 AND t3.feature_code = 'ADM3'
WHERE
(t0.feature_class IN ('P', 'A') OR (t0.feature_class = 'L' AND t0.feature_code = 'RGN' ) )
AND t0.name like 'Cornwall%'
GROUP BY CONCAT_WS(', ', t0.name,
IF(t3.name != t0.name, t3.name, NULL),
IF(t2.name != t0.name, t2.name, NULL),
IF(t1.name != t0.name, t1.name, NULL))
ORDER BY t0.name
它返回错误的记录：
id | name
---------------------------
2652355 | Cornwall, England
答案 0 :(得分：1)
我认为条件聚合应该可以解决问题。您可以按name过滤记录，然后在集合函数中应用逻辑。如果记录中有feature_code = 'RGN'，则您要选择它，否则您将在匹配的记录中选择最小的id。
SELECT IFNULL(MAX(CASE WHEN feature_code = 'RGN' THEN id END), MIN(id)) id_found
FROM mytable
WHERE name = @name;
'Cornwall'时
| id_found |
| -------- |
| 11609029 |
注意：如果您想要整个匹配的记录，一种解决方案是简单地将上述结果集与原始表进行JOIN：
SELECT t.*
FROM mytable t
INNER JOIN (
SELECT IFNULL(MAX(CASE WHEN feature_code = 'RGN' THEN id END), MIN(id)) id_found
FROM mytable
WHERE name = @name
) x ON x.id_found = t.id;
Demo ：
| id | name | admin1 | admin2 | admin3 | feature_class | feature_code |
| -------- | -------- | ------ | ------ | ------ | ------------- | ------------ |
| 11609029 | Cornwall | ENG | | | L | RGN |
答案 1 :(得分：0)
在MySQL中，您可以使用相关子查询：
window.addEventListener('load', () => {
// Determine whether you are going first
const humanTurnFirst = Math.random() >= 0.5;
/**
* Get an array of the text content of each of the tic-tac-toe buttons
* @returns {Array} Array of the text content of each square, from top-left to bottom-right.
*/
const getLayout = () => {
// Array of buttons ordered from top-left to bottom right
const buttons = [
document.getElementsByClassName('corner-top-left')[0],
document.getElementsByClassName('edge-top')[0],
document.getElementsByClassName('corner-top-right')[0],
document.getElementsByClassName('edge-left')[0],
document.getElementsByClassName('center-button')[0],
document.getElementsByClassName('edge-right')[0],
document.getElementsByClassName('corner-bottom-left')[0],
document.getElementsByClassName('edge-bottom')[0],
document.getElementsByClassName('corner-bottom-right')[0],
];
const layout = [];
buttons.forEach(button => layout.push(button.innerText));
return layout;
};
/**
* Make the computer play a square
* @param {Node} button The square to play
*/
const autoClick = (button) => {
console.log('button', button);
const $turn = document.getElementsByClassName('turn')[0];
$turn.innerText = 'Not your turn yet...';
const $allButtons = [...document.getElementsByClassName('button')];
const $allDisableableButtons = $allButtons
.filter(
element => element !== button
&& !element.disabled,
);
$allDisableableButtons.forEach((disableableButton) => {
const thisButton = disableableButton;
thisButton.disabled = true;
});
console.log('button', button);
button.focus();
setTimeout(() => {
button.click();
$allDisableableButtons.forEach((disableableButton) => {
const thisButton = disableableButton;
thisButton.disabled = false;
$turn.innerText = 'Try clicking an empty space.';
});
}, 500);
};
/**
* Calculate the best square for the computer to play.
* @param {Array.<Node>} layout Array of the text of each square, from top-left to bottom right.
* @param {Node|Boolean} previous The last move that you've made.
*/
const computerTurn = (layout, previous, localHumanTurnFirst) => {
const buttons = [
document.getElementsByClassName('corner-top-left')[0],
document.getElementsByClassName('edge-top')[0],
document.getElementsByClassName('corner-top-right')[0],
document.getElementsByClassName('edge-left')[0],
document.getElementsByClassName('center-button')[0],
document.getElementsByClassName('edge-right')[0],
document.getElementsByClassName('corner-bottom-left')[0],
document.getElementsByClassName('edge-bottom')[0],
document.getElementsByClassName('corner-bottom-right')[0],
];
const $corners = [...document.getElementsByClassName('corner')];
// If there is no previous move, the computer goes first with a random corner.
if (!previous) {
const randomBelow4 = Math.floor(Math.random() * 4);
const randomCorner = $corners[randomBelow4];
autoClick(randomCorner);
/* If the computer is going first,
has already filled out a random corner,
and there is nothing in the center,
it will place another X in one of the adgacent corners.
*/
} else if (
!localHumanTurnFirst
&& layout.filter(element => element === 'X').length === 1
&& previous !== buttons[4]
) {
const filledOutCorner = buttons.filter(element => element.innerText === 'X')[0];
const diagonalCorner = document.getElementsByClassName(filledOutCorner.className
.split(/\s+/)[2]
.replace(/(left|right)/, match => (match === 'left' ? 'right' : 'left'))
.replace(/(top|bottom)/, match => (match === 'top' ? 'bottom' : 'top')))[0];
const emptyCorners = $corners.filter(corner => corner.innerText === 'Empty');
const adjacentCorners = emptyCorners.filter(element => element !== diagonalCorner);
const potentialCorners = adjacentCorners
.filter(
corner => document.getElementsByClassName(`edge-${corner.className.split(/\s+/)[2].split('-')[1]}`)[0].innerText === 'Empty'
&& document.getElementsByClassName(`edge-${corner.className.split(/\s+/)[2].split('-')[2]}`)[0].innerText === 'Empty',
);
const randomPotentialCorner = potentialCorners[
Math.floor(
Math.random()
* potentialCorners.length,
)
];
autoClick(randomPotentialCorner);
} else if (
!localHumanTurnFirst
&& buttons.filter(button => button.innerText === 'X' && button.className.split(/\s+/).includes('corner')).length === 2
&& buttons.filter(button => button.innerText === 'O' && [...document.getElementsByClassName(`corner-${button.className.replace('button edge edge-', '')}`)].every(element => element.innerText === 'X')).length === 1
) {
autoClick(buttons[4]);
}
};
/**
* Add event listener for squares
* @param {Boolean} localHumanTurnFirst Whether you go first.
*/
const squaresOnClick = (localHumanTurnFirst, isHumanTurn) => {
const humanLetter = localHumanTurnFirst ? 'X' : 'O';
const computerLetter = localHumanTurnFirst ? 'O' : 'X';
const $squares = [...document.getElementsByClassName('button')];
$squares.forEach((square) => {
const thisSquare = square;
square.addEventListener('click', () => {
if (isHumanTurn) {
thisSquare.innerText = humanLetter;
computerTurn(getLayout(), thisSquare, localHumanTurnFirst);
squaresOnClick(localHumanTurnFirst, false);
} else {
thisSquare.innerText = computerLetter;
squaresOnClick(localHumanTurnFirst, true);
}
thisSquare.disabled = true;
});
});
};
/**
* Turn the welcome screen into the game screen.
* @param {Boolean} localHumanTurnFirst Whether you go first.
*/
const spawnSquares = (localHumanTurnFirst) => {
const $turn = document.getElementsByClassName('turn')[0];
const $mainGame = document.getElementsByClassName('main-game')[0];
$turn.innerText = 'Try clicking an empty space.';
$mainGame.className = 'main-game dp-4 tic-tac-toe';
$mainGame.setAttribute('aria-label', 'Tic-tac-toe grid');
$mainGame.innerHTML = `
<button class="button corner corner-top-left corner-top corner-left">Empty</button>
<button class="button edge edge-top">Empty</button>
<button class="button corner corner-top-right corner-top corner-right">Empty</button>
<button class="button edge edge-left">Empty</button>
<button class="button center-button">Empty</button>
<button class="button edge edge-right">Empty</button>
<button class="button corner corner-bottom-left corner-bottom corner-left">Empty</button>
<button class="button edge edge-bottom">Empty</button>
<button class="button corner corner-bottom-right corner-bottom corner-right">Empty</button>
`;
squaresOnClick(localHumanTurnFirst, localHumanTurnFirst);
if (!localHumanTurnFirst) {
computerTurn(getLayout(), false, localHumanTurnFirst);
}
};
/**
* Create the button that starts the game.
*/
const welcomeButton = (localHumanTurnFirst) => {
const $welcomeButton = document.getElementsByClassName('start-button')[0];
$welcomeButton.addEventListener('click', () => spawnSquares(localHumanTurnFirst));
};
/**
* Turn the main game into the welcome screen.
* @param {Boolean} localHumanTurnFirst Whether you go first.
*/
const welcome = (localHumanTurnFirst) => {
const $mainGame = document.getElementsByClassName('main-game')[0];
const $turn = document.getElementsByClassName('turn')[0];
$turn.innerText = 'Welcome!';
$mainGame.className = 'main-game dp-4 welcome center';
$mainGame.innerHTML = `
<section class="welcome-section">
<h2 class="welcome-heading">Welcome to unbeatable tic-tac-toe!</h2>
<p class="welcome-text">
According to random chance, your turn has already been chosen
as ${localHumanTurnFirst ? 'first (with an X)' : 'second (with an O)'}, which
means that the computer is going
${localHumanTurnFirst ? 'second (with an O)' : 'first (with an X)'}. <strong>
Press the start button to start the game!</strong
>
</p>
</section>
<button class="start-button button">Start</button>
`;
welcomeButton(localHumanTurnFirst);
};
welcome(humanTurnFirst);
});
在MySQL 8+中，您还可以使用 } else if (
!localHumanTurnFirst
&& layout.filter(element => element === 'X').length === 1
&& previous !== buttons[4]
) {
const filledOutCorner = buttons.filter(element => element.innerText === 'X')[0];
const diagonalCorner = document.getElementsByClassName(filledOutCorner.className
.split(/\s+/)[2]
.replace(/(left|right)/, match => (match === 'left' ? 'right' : 'left'))
.replace(/(top|bottom)/, match => (match === 'top' ? 'bottom' : 'top')))[0];
const emptyCorners = $corners.filter(corner => corner.innerText === 'Empty');
const adjacentCorners = emptyCorners.filter(element => element !== diagonalCorner);
const potentialCorners = adjacentCorners
.filter(
corner => document.getElementsByClassName(`edge-${corner.className.split(/\s+/)[2].split('-')[1]}`)[0].innerText === 'Empty'
&& document.getElementsByClassName(`edge-${corner.className.split(/\s+/)[2].split('-')[2]}`)[0].innerText === 'Empty',
);
const randomPotentialCorner = potentialCorners[
Math.floor(
Math.random()
* potentialCorners.length,
)
];
autoClick(randomPotentialCorner);
} else if (
!localHumanTurnFirst
&& buttons.filter(button => button.innerText === 'X' && button.className.split(/\s+/).includes('corner')).length === 2
&& buttons.filter(button => button.innerText === 'O' && [...document.getElementsByClassName(`corner-${button.className.replace('button edge edge-', '')}`)].every(element => element.innerText === 'X')).length === 1
) {
autoClick(buttons[4]);
}
：
select l.*
from locations l
where l.id = (select l2.id
from locations l2
where l2.name = l.name
order by (feature_code = 'RGN') desc, -- put regions first
id asc
);
答案 2 :(得分：0)
可能存在一种方法，并将所有方法合并在一起
select t1.* from location t1
where exists ( select 1 from location t2 where t2.name=t1.name and t2.feature_code='RGN'
)
and t1.feature_code='RGN'
union all
select t1.* from location t1
where not exists ( select 1 from location t2 where t2.name=t1.name and
t2.feature_code='RGN'
)
and t1.id=(select min(id) from location t2 where t2.name=t1.name)