刪除外鍵使用變量名

我使用以下命令：刪除外鍵使用變量名

DECLARE @ConstraintName varchar(255); 
SELECT @ConstraintName = CONSTRAINT_NAME 
FROM 
    INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE 
WHERE 
    TABLE_NAME = 'TheTable' 
    AND COLUMN_NAME = 'TheColumn'; 

alter table TheTable drop constraint @ConstraintName;

但是，它有@ConstraintName附近的語法不正確。這可能是一件小事，但我無法弄清楚。我應該改變什麼，這樣約束會被刪除？

SQLFiddle：http://sqlfiddle.com/#!2/6709e/3

來源

2014-05-20 Joetjah

Isn「t it SELECT INTO @ConstraintName ... ??? –

@AnthonyRaymond給了我'關鍵字'INTO'附近的語法不正確。 – Joetjah

DECLARE @constraintName VARCHAR(50); 
DECLARE @runString VARCHAR(2000); 

select @constraintName = CONSTRAINT_NAME 
from INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE 
WHERE TABLE_NAME = 'TheTable' AND COLUMN_NAME = 'TheColumn'; 


SET @runString = 'ALTER TABLE TheTable DROP CONSTRAINT ' + @constraintName; 
EXECUTE (@runString);

來源

2014-05-20 11:46:10 Joetjah

'添加約束'，但'放棄外鍵' –

'concat'，而不是'+' –

試試這個：

DECLARE @ConstraintName VARCHAR(255); 
SELECT CONSTRAINT_NAME 
INTO @ConstraintName 
FROM 
    INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE 
WHERE 
    TABLE_NAME = 'TheTable' 
    AND COLUMN_NAME = 'TheColumn'; 

alter table TheTable drop constraint @ConstraintName;

或者：

DECLARE @ConstraintName VARCHAR(255); 
SELECT @ConstraintName:=CONSTRAINT_NAME 
FROM 
    INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE 
WHERE 
    TABLE_NAME = 'TheTable' 
    AND COLUMN_NAME = 'TheColumn'; 

alter table TheTable drop constraint @ConstraintName;

來源

2014-05-20 10:41:17

他們沒有工作。第一個在@ConstraintName附近有不正確的語法，第二個在'：'附近有不正確的語法。 – Joetjah

@Joetjah你可以創建一個SQLFiddle，這樣我們可以自己做一些測試嗎？ http://sqlfiddle.com/ –

@Joetjah plus，你在哪裏測試你的請求？命令行，PhpMyAdmin，工作臺，...？ –

試試這個

SELECT CONSTRAINT_NAME INTO @ConstraintName 
FROM 
    INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE 
WHERE 
    TABLE_NAME = 'TheTable' 
    AND COLUMN_NAME = 'TheColumn'; 

SET @queryStr = CONCAT('alter table TheTable drop constraint ', @ConstraintName); 
PREPARE qry from @queryStr; 
EXECUTE qry;

欲瞭解更多信息：https://dev.mysql.com/doc/refman/5.7/en/execute.html

來源

2017-05-22 05:52:59 srsajid

刪除外鍵使用變量名

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