サブクエリでのGROUP_CONCATの奇妙な結果

あなたの質問は少し奇妙です。

select name, GROUP_CONCAT(DISTINCT(id) SEPARATOR "-") AS id FROM (
        (select "APN" AS name, GROUP_CONCAT(DISTINCT(site.id) SEPARATOR "-") AS id  from site WHERE id IN (138,147,8918,8916,9033,9240,97,9038,8886,9036,9067,146,37,9127,52,9031,23,8635,8665,46,39,18,33,9035,137,9051,8766,25,20,9160,133,8636,9021,8655,21,42,8757,22,9017,77,9037,44,49,9323,55,74,150,8,67,1,8928,58,9025,9221,9019,9069,9214,9176,95,40,9335,168,9260,8641,9227,9258,24,50,29,9073,12,36,8882,9,43,76,9032,51,9060,96,8922,9212,14,9095,28,9213,31,41,68,9027,8884,9023,9059,9034,9016,11,61,9229,8761,9225,8937,9018,9121,9119,8659,8926,9096,57,9083,8662,9232,149,8643,88,19,8660,10,8936,9210,9241,17,8872)) 
    UNION ALL 
        (select "smart" AS name, GROUP_CONCAT(DISTINCT(site.id) SEPARATOR "-") AS id from site WHERE id IN (9129,8981,9136,9169,9170,9171,9172,9297,9147,9155,9139,9138,9142,9296,8987,9216,9252,9320,8951,8945,8952,8965,8963,9012,9192,8938,8941,8968,8977,9117,9135,9140,9143,9295,9298,9137,8988,8989,8992,9164,9156,9165,9168,9173,8953,8999,8939,8940,8942,8943,8954,8956,8957,8959,8960,8964,8971,8972,8973,8974,8982,9000,9001,9003,8950,8978,8979,8983,9002,9005,8984,8955,8986,8980,8993,9008,9010,8949,8998,9150,9122,8944,8946,8948,9006,9009,9013,9128,9215,9321,9011,9154,8970,8975,8994,9070,8966,8958,9007,9014))
) t GROUP BY name;

等しい：

    (select "APN" AS name, GROUP_CONCAT(DISTINCT(site.id) SEPARATOR "-") AS id  from site WHERE id IN (138,147,8918,8916,9033,9240,97,9038,8886,9036,9067,146,37,9127,52,9031,23,8635,8665,46,39,18,33,9035,137,9051,8766,25,20,9160,133,8636,9021,8655,21,42,8757,22,9017,77,9037,44,49,9323,55,74,150,8,67,1,8928,58,9025,9221,9019,9069,9214,9176,95,40,9335,168,9260,8641,9227,9258,24,50,29,9073,12,36,8882,9,43,76,9032,51,9060,96,8922,9212,14,9095,28,9213,31,41,68,9027,8884,9023,9059,9034,9016,11,61,9229,8761,9225,8937,9018,9121,9119,8659,8926,9096,57,9083,8662,9232,149,8643,88,19,8660,10,8936,9210,9241,17,8872)) 
    UNION ALL 
    (select "smart" AS name, GROUP_CONCAT(DISTINCT(site.id) SEPARATOR "-") AS id from site WHERE id IN (9129,8981,9136,9169,9170,9171,9172,9297,9147,9155,9139,9138,9142,9296,8987,9216,9252,9320,8951,8945,8952,8965,8963,9012,9192,8938,8941,8968,8977,9117,9135,9140,9143,9295,9298,9137,8988,8989,8992,9164,9156,9165,9168,9173,8953,8999,8939,8940,8942,8943,8954,8956,8957,8959,8960,8964,8971,8972,8973,8974,8982,9000,9001,9003,8950,8978,8979,8983,9002,9005,8984,8955,8986,8980,8993,9008,9010,8949,8998,9150,9122,8944,8946,8948,9006,9009,9013,9128,9215,9321,9011,9154,8970,8975,8994,9070,8966,8958,9007,9014))

元のクエリで同じIDのグループを持つ多数のAPN行が生成されない限り、名前とIDで親をグループ化する必要はありません。

質問に戻る ：group_concatの最大長は1024ですが、sort / union操作はさらに1/3（1024/3 =341）に切り捨てられます。（既知ですが、これをバックアップするための公式文書はありません）

あなたの場合、グループ連結の最大長の値を増やすだけです：

SET group_concat_max_len = 5000;

これにより、切り捨てることなく目的の出力が得られるはずです。

一時テーブルを作成してそれらを結合するか、grou_concatの結果を変数に出力することができます。どちらの場合も、grop_concatは元のデフォルト値で切り捨てられます。