21 lines
508 B
SQL
21 lines
508 B
SQL
-- 只有当 ads 表中不存在 description 字段时才添加
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SET
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@col_exists := (
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SELECT COUNT(*)
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FROM INFORMATION_SCHEMA.COLUMNS
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WHERE TABLE_SCHEMA = DATABASE()
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AND TABLE_NAME = 'ads'
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AND COLUMN_NAME = 'description'
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);
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SET
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@query := IF(
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@col_exists = 0,
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'ALTER TABLE `ads` ADD COLUMN `description` VARCHAR(255) DEFAULT '''' COMMENT ''Description'';',
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'SELECT "Column `description` already exists"'
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);
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PREPARE stmt FROM @query;
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EXECUTE stmt;
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DEALLOCATE PREPARE stmt;
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