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MySQL JOIN与LEFT JOIN的区别(Difference in MySQL JOIN vs LEFT JOIN)

 我有这个跨数据库查询...  
SELECT
            `DM_Server`.`Jobs`.*,
            `DM_Server`.servers.Description AS server,
            digital_inventory.params,
            products.products_id,
            products.products_pdfupload,
            customers.customers_firstname,
            customers.customers_lastname
        FROM `DM_Server`.`Jobs`
        INNER JOIN `DM_Server`.servers ON servers.ServerID = Jobs.Jobs_ServerID
        JOIN `cpod_live`.`digital_inventory` ON digital_inventory.jobname = Jobs.Jobs_Name
        JOIN `cpod_live`.`products` ON products.products_pdfupload = CONCAT(digital_inventory.jobname, ".pdf")
        JOIN `cpod_live`.`customers` ON customers.customers_id = products.cID
        ORDER BY `DM_Server`.`Jobs`.Jobs_StartTime DESC LIMIT 50
 
 它运行良好，直到我让他们LEFT JOIN 。 我以为没有指定一种类型的连接，它被认为是一个LEFT JOIN 。 不是这样吗？ 

I have this cross-database query... 
SELECT
            `DM_Server`.`Jobs`.*,
            `DM_Server`.servers.Description AS server,
            digital_inventory.params,
            products.products_id,
            products.products_pdfupload,
            customers.customers_firstname,
            customers.customers_lastname
        FROM `DM_Server`.`Jobs`
        INNER JOIN `DM_Server`.servers ON servers.ServerID = Jobs.Jobs_ServerID
        JOIN `cpod_live`.`digital_inventory` ON digital_inventory.jobname = Jobs.Jobs_Name
        JOIN `cpod_live`.`products` ON products.products_pdfupload = CONCAT(digital_inventory.jobname, ".pdf")
        JOIN `cpod_live`.`customers` ON customers.customers_id = products.cID
        ORDER BY `DM_Server`.`Jobs`.Jobs_StartTime DESC LIMIT 50
 
it runs fine until I make them LEFT JOINs. I thought that by not specifying a type of join it was assumed to be a LEFT JOIN. Is this not the case?

原文：https://stackoverflow.com/questions/9770366

更新时间：2022-03-17 11:03

最满意答案

 
 
  
  var arr=[{
    "no": "1",
    "location": "Acheh Baru",
    "postcode": "32000",
    "postOffice": "Sitiawan",
    "state": "Perak"
}, {
    "no": "2",
    "location": "Akauntan Negeri",
    "postcode": "30594",
    "postOffice": "Ipoh",
    "state": "Perak"
}, {
    "no": "3",
    "location": "Alor Kechor",
    "postcode": "32800",
    "postOffice": "Parit",
    "state": "Perak"
}];

function findObjectByKey(array, key, value) {
    for (var i = 0; i < array.length; i++) {
        if (array[i][key] === value) {
            return array[i]['location'];
        }
    }
    return null;
}

var obj = findObjectByKey(arr, 'no', "3");

console.log(obj); 
  
 

 
 
  
  var arr=[{
    "no": "1",
    "location": "Acheh Baru",
    "postcode": "32000",
    "postOffice": "Sitiawan",
    "state": "Perak"
}, {
    "no": "2",
    "location": "Akauntan Negeri",
    "postcode": "30594",
    "postOffice": "Ipoh",
    "state": "Perak"
}, {
    "no": "3",
    "location": "Alor Kechor",
    "postcode": "32800",
    "postOffice": "Parit",
    "state": "Perak"
}];

function findObjectByKey(array, key, value) {
    for (var i = 0; i < array.length; i++) {
        if (array[i][key] === value) {
            return array[i]['location'];
        }
    }
    return null;
}

var obj = findObjectByKey(arr, 'no', "3");

console.log(obj);

MySQL JOIN与LEFT JOIN的区别(Difference in MySQL JOIN vs LEFT JOIN)

最满意答案

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