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class=\"replaceable\"><code>n</code></em>)</code> 或\n    <code class=\"type\">character(<em class=\"replaceable\"><code>n</code></em>)</code>，那么超长的值会被截断为 <em class=\"replaceable\"><code>n</code></em> 个字符而不会报错。（这同样是 <acronym class=\"acronym\">SQL</acronym> 标准要求的。）如果要存储的字符串短于声明长度，<code class=\"type\">character</code> 类型的值会用空格填充；<code class=\"type\">character varying</code> 类型则只是简单地存储较短的字符串。\n   </p><p>\n    此外，<span class=\"productname\">PostgreSQL</span> 还提供\n    <code class=\"type\">text</code> 类型，用于存储任意长度的字符串。虽然\n    <code class=\"type\">text</code> 类型不在 <acronym class=\"acronym\">SQL</acronym> 标准中，但其他若干 SQL 数据库管理系统也提供了它。<code class=\"type\">text</code> 是\n    <span class=\"productname\">PostgreSQL</span> 的原生字符串数据类型，因为大多数对字符串进行操作的内置函数都声明为接受或返回\n    <code class=\"type\">text</code>，而不是 <code class=\"type\">character varying</code>。在很多场景下，<code class=\"type\">character varying</code> 的行为就像是建立在\n    <code class=\"type\">text</code> 之上的一个<a class=\"link\" href=\"/zh/docs/18/domains.html\">域</a>。\n   </p><p>\n    类型名 <code class=\"type\">varchar</code> 是 <code class=\"type\">character varying</code> 的别名，而 <code class=\"type\">bpchar</code>（带长度说明时）和 <code class=\"type\">char</code>\n    是 <code class=\"type\">character</code> 的别名。<code class=\"type\">varchar</code> 和\n    <code class=\"type\">char</code> 这两个别名由 <acronym class=\"acronym\">SQL</acronym> 标准定义；<code class=\"type\">bpchar</code> 则是 <span class=\"productname\">PostgreSQL</span>\n    的扩展。\n   </p><p><a href=\"/zh/docs/18/datatype-character.html\">查看完整中文手册与上下文</a>。</p>"}, "summary": "变长字符串", "version": "18", "link_map": {"/zh/docs/18/domains.html": "/docs/18/domains.html", "/zh/docs/18/datatype-character.html": "/docs/18/datatype-character.html", "/zh/docs/18/datatype-character.html#DATATYPE-CHARACTER-TABLE": "/docs/18/datatype-character.html#DATATYPE-CHARACTER-TABLE"}, "body_html": "<p>变长字符串</p><h3>同版本中文手册节选</h3><p>\n<a href=\"/zh/docs/18/datatype-character.html#DATATYPE-CHARACTER-TABLE\" rel=\"nofollow\">表 8.4</a> 显示了在 <span>PostgreSQL</span> 里可用的一般用途的字符类型。\n   </p><p>\n<acronym>SQL</acronym> 定义了两种主要字符类型：<code>character varying(<em><code>n</code></em>)</code> 和\n    <code>character(<em><code>n</code></em>)</code>，其中\n    <em><code>n</code></em> 是正整数。这两种类型都可以存储长度最多为 <em><code>n</code></em> 个字符（而不是字节）的字符串。试图把更长的字符串存入这些类型的列时会报错，除非超出的字符全部都是空格，在这种情况下字符串会被截断到最大长度。（这一多少有些奇怪的例外是 <acronym>SQL</acronym> 标准要求的。）不过，如果显式把一个值转换为\n    <code>character varying(<em><code>n</code></em>)</code> 或\n    <code>character(<em><code>n</code></em>)</code>，那么超长的值会被截断为 <em><code>n</code></em> 个字符而不会报错。（这同样是 <acronym>SQL</acronym> 标准要求的。）如果要存储的字符串短于声明长度，<code>character</code> 类型的值会用空格填充；<code>character varying</code> 类型则只是简单地存储较短的字符串。\n   </p><p>\n    此外，<span>PostgreSQL</span> 还提供\n    <code>text</code> 类型，用于存储任意长度的字符串。虽然\n    <code>text</code> 类型不在 <acronym>SQL</acronym> 标准中，但其他若干 SQL 数据库管理系统也提供了它。<code>text</code> 是\n    <span>PostgreSQL</span> 的原生字符串数据类型，因为大多数对字符串进行操作的内置函数都声明为接受或返回\n    <code>text</code>，而不是 <code>character varying</code>。在很多场景下，<code>character varying</code> 的行为就像是建立在\n    <code>text</code> 之上的一个<a href=\"/zh/docs/18/domains.html\" rel=\"nofollow\">域</a>。\n   </p><p>\n    类型名 <code>varchar</code> 是 <code>character varying</code> 的别名，而 <code>bpchar</code>（带长度说明时）和 <code>char</code>\n    是 <code>character</code> 的别名。<code>varchar</code> 和\n    <code>char</code> 这两个别名由 <acronym>SQL</acronym> 标准定义；<code>bpchar</code> 则是 <span>PostgreSQL</span>\n    的扩展。\n   </p><p><a href=\"/zh/docs/18/datatype-character.html\" rel=\"nofollow\">查看完整中文手册与上下文</a>。</p>", "body_sha256": "0a667a63ff15cf37b6bc50565c74a2ee2ab83c64a7ebd11314a6a1526a3ced31", "content_hash": "28834f557d94897b5d3d97b2280f13228a53dce21821470c7fe78c0f802e4db9", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "operators": [], "signature": "character varying [ ( n ) 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<code>character(<em><code>n</code></em>)</code>，那么超长的值会被截断为 <em><code>n</code></em> 个字符而不会报错。（这同样是 <acronym>SQL</acronym> 标准要求的。）如果要存储的字符串短于声明长度，<code>character</code> 类型的值会用空格填充；<code>character varying</code> 类型则只是简单地存储较短的字符串。\n   </p><p>\n    此外，<span>PostgreSQL</span> 还提供\n    <code>text</code> 类型，用于存储任意长度的字符串。虽然\n    <code>text</code> 类型不在 <acronym>SQL</acronym> 标准中，但其他若干 SQL 数据库管理系统也提供了它。<code>text</code> 是\n    <span>PostgreSQL</span> 的原生字符串数据类型，因为大多数对字符串进行操作的内置函数都声明为接受或返回\n    <code>text</code>，而不是 <code>character varying</code>。在很多场景下，<code>character varying</code> 的行为就像是建立在\n    <code>text</code> 之上的一个<a href=\"/zh/docs/18/domains.html\" rel=\"nofollow\">域</a>。\n   </p><p>\n    类型名 <code>varchar</code> 是 <code>character varying</code> 的别名，而 <code>bpchar</code>（带长度说明时）和 <code>char</code>\n    是 <code>character</code> 的别名。<code>varchar</code> 和\n    <code>char</code> 这两个别名由 <acronym>SQL</acronym> 标准定义；<code>bpchar</code> 则是 <span>PostgreSQL</span>\n    的扩展。\n   </p><p><a href=\"/zh/docs/18/datatype-character.html\" rel=\"nofollow\">查看完整中文手册与上下文</a>。</p>", "manual_documentation": "dedicated family chapter", "center_zh_rendered": "<p>变长字符串</p><h3>同版本中文手册节选</h3><p>\n<a href=\"/docs/18/datatype-character.html#DATATYPE-CHARACTER-TABLE\">表 8.4</a> 显示了在 <span>PostgreSQL</span> 里可用的一般用途的字符类型。\n   </p><p>\nSQL 定义了两种主要字符类型：<code>character varying(<em><code>n</code></em>)</code> 和\n    <code>character(<em><code>n</code></em>)</code>，其中\n    <em><code>n</code></em> 是正整数。这两种类型都可以存储长度最多为 <em><code>n</code></em> 个字符（而不是字节）的字符串。试图把更长的字符串存入这些类型的列时会报错，除非超出的字符全部都是空格，在这种情况下字符串会被截断到最大长度。（这一多少有些奇怪的例外是 SQL 标准要求的。）不过，如果显式把一个值转换为\n    <code>character varying(<em><code>n</code></em>)</code> 或\n    <code>character(<em><code>n</code></em>)</code>，那么超长的值会被截断为 <em><code>n</code></em> 个字符而不会报错。（这同样是 SQL 标准要求的。）如果要存储的字符串短于声明长度，<code>character</code> 类型的值会用空格填充；<code>character varying</code> 类型则只是简单地存储较短的字符串。\n   </p><p>\n    此外，<span>PostgreSQL</span> 还提供\n    <code>text</code> 类型，用于存储任意长度的字符串。虽然\n    <code>text</code> 类型不在 SQL 标准中，但其他若干 SQL 数据库管理系统也提供了它。<code>text</code> 是\n    <span>PostgreSQL</span> 的原生字符串数据类型，因为大多数对字符串进行操作的内置函数都声明为接受或返回\n    <code>text</code>，而不是 <code>character varying</code>。在很多场景下，<code>character varying</code> 的行为就像是建立在\n    <code>text</code> 之上的一个<a href=\"/docs/18/domains.html\">域</a>。\n   </p><p>\n    类型名 <code>varchar</code> 是 <code>character varying</code> 的别名，而 <code>bpchar</code>（带长度说明时）和 <code>char</code>\n    是 <code>character</code> 的别名。<code>varchar</code> 和\n    <code>char</code> 这两个别名由 SQL 标准定义；<code>bpchar</code> 则是 <span>PostgreSQL</span>\n    的扩展。\n   </p><p><a href=\"/docs/18/datatype-character.html\">查看完整中文手册与上下文</a>。</p>"}, "from": "17", "comparison": {"available": true, "changes": [], "prose_changed": false}}